/* pdp11_vh.c: DHQ11 asynchronous terminal multiplexor simulator

   Copyright (c) 2004-2022, John A. Dundas III
   Portions derived from work by Robert M Supnik

   Permission is hereby granted, free of charge, to any person obtaining a
   copy of this software and associated documentation files (the "Software"),
   to deal in the Software without restriction, including without limitation
   the rights to use, copy, modify, merge, publish, distribute, sublicense,
   and/or sell copies of the Software, and to permit persons to whom the
   Software is furnished to do so, subject to the following conditions:

   The above copyright notice and this permission notice shall be included in
   all copies or substantial portions of the Software.

   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
   THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

   Except as contained in this notice, the name of the Author shall not be
   used in advertising or otherwise to promote the sale, use or other dealings
   in this Software without prior written authorization from the Author.

   vh           DHQ11 asynch multiplexor for SIMH

   23-Jul-22    JAD     Correct RBUF_GETLINE & RBUF_PUTLINE: these are both
                        sensitive to modeling DHU vs. DHV; the correct bit
                        mask was not generated for DHU.
                        Make certain the device presents 16 lines when
                        modeling a DHU.
                        In vh_reset(), make certain the number of lines
                        makes sense in the context of the current bus
                        and adjust if not appropriate; mark each unit
                        correctly for DHU vs. DHV; mark each unit
                        enabled or disabled as appropriate; reset
                        the vector length; reset the number of units.

                        Retrofit updates from V4 SIMH: (Mark Pizzolato)
                        VH_LINES must be set according to the bus type
                        (Unibus: 16, Qbus: 8).
                        Define VH_LINES_ALLOC at 16 lines/unit to reserve
                        the maximum space for lines.
                        SET VH LINES=n is now sensitive to mode; appropriate
                        values are DHV: 8, 16, 24, 32; DHU: 16, 32, 48, 64
                        In fifo_get(), sense immediately when the FIFO
                        empties, rather than the next time through.
                        In vh_setnl(), call vh_reset () to adjust the state
                        of the units and lines, and invoke auto_config().
   28-May-18    RMS     Changed to avoid nested comment warnings (Mark Pizzolato)
   02-Jun-11    MP      Added debugging support to trace register, interrupt 
                        and data traffic (SET VH DEBUG[=REG;INT;XMT;RCV])
                        Added SET LOG and SET NOLOG support for logging mux
                        traffic
                        Fixed SET VH LINES=n to correctly adjust the number
                        of lines available to be 8, 16, 24, or 32.
                        Fixed performance issue avoiding redundant polling
   03-Jan-10    JAD     Eliminate gcc warnings
   24-Nov-08    JDB     Removed tmxr_send_buffered_data declaration (now in sim_tmxr.h)
   19-Nov-08    RMS     Revised for common TMXR show routines
   18-Jun-07    RMS     Added UNIT_IDLE flag
   29-Oct-06    RMS     Synced poll and clock
   07-Jul-05    RMS     Removed extraneous externs
   15-Jun-05    RMS     Revised for new autoconfigure interface
                        Fixed bug in vector display routine
   12-Jun-04    RMS     Repair MS2SIMH macro to avoid divide by 0 bug
   08-Jun-04    JAD     Repair vh_dev initialization; remove unused
                        variables, cast to avoid conversion confusion
   07-Jun-04    JAD     Complete function prototypes of forward declarations.
                        Repair broken prototypes of vh_rd() and vh_wr()
                        Explicitly size integer declarations
   4-Jun-04     JAD     Preliminary code: If operating in a PDP-11 Unibus
                        environment, force DHU mode
   29-May-04    JAD     Make certain RX.TIMER is within allowable range
   25-May-04    JAD     All time-based operations are scaled by tmxr_poll units
   23-May-04    JAD     Change to fifo_get() and dq_tx_report() to avoid
                        gratuitous stack manipulation
   20-May-04    JAD     Made modem control and auto-hangup unit flags
   19-May-04    JAD     Fix problem with modem status where the line number
                        was not being included
   12-May-04    JAD     Revised for updated tmxr interfaces
   28-Jan-04    JAD     Original creation and testing

I/O Page Registers

CSR 17 760 440 (float)

Vector: 300 (float)

Priority:   BR4

Rank:       32

*/
/* MANY constants needed! */

#if defined (VM_VAX)
#include "vax_defs.h"
extern int32    int_req[IPL_HLVL];
#endif

#if defined (VM_PDP11)
#include "pdp11_defs.h"
extern int32    int_req[IPL_HLVL];
extern uint32    cpu_opt;
#endif

#include "sim_tmxr.h"

/* imports from pdp11_stddev.c: */
extern int32    tmxr_poll, clk_tps;
/* convert ms to SIMH time units based on tmxr_poll polls per second */
#define MS2SIMH(ms) (((ms) * clk_tps) / 1000)

#ifndef VH_MUXES
#define VH_MUXES    (4)
#endif
#define VH_MNOMASK  (VH_MUXES - 1)

#if defined(VM_VAX)
#if VEC_QBUS
#define VH_LINES    (8)
#else
#define VH_LINES    (16)
#endif
#else
#define VH_LINES    (UNIBUS?16:8)
#endif

#define VH_LINES_ALLOC (16)

#define UNIT_V_MODEDHU  (UNIT_V_UF + 0)
#define UNIT_V_FASTDMA  (UNIT_V_UF + 1)
#define UNIT_V_MODEM    (UNIT_V_UF + 2)
#define UNIT_V_HANGUP   (UNIT_V_UF + 3)
#define UNIT_MODEDHU    (1 << UNIT_V_MODEDHU)
#define UNIT_FASTDMA    (1 << UNIT_V_FASTDMA)
#define UNIT_MODEM  (1 << UNIT_V_MODEM)
#define UNIT_HANGUP (1 << UNIT_V_HANGUP)

/* VHCSR - 160440 - Control and Status Register */

#define CSR_M_IND_ADDR      (017)
#define CSR_SKIP        (1 << 4)
#define CSR_MASTER_RESET    (1 << 5)
#define CSR_RXIE        (1 << 6)
#define CSR_RX_DATA_AVAIL   (1 << 7)
#define CSR_M_TX_LINE       (017)
#define CSR_V_TX_LINE       (8)
#define CSR_TX_DMA_ERR      (1 << 12)
#define CSR_DIAG_FAIL       (1 << 13)
#define CSR_TXIE        (1 << 14)
#define CSR_TX_ACTION       (1 << 15)
#define CSR_GETCHAN(x)  ((x) & CSR_M_IND_ADDR)
#define CSR_RW          \
    (CSR_TXIE|CSR_RXIE|CSR_SKIP|CSR_M_IND_ADDR|CSR_MASTER_RESET)
#define RESET_ABORT     (052525)

/* Receive Buffer (RBUF) */

#define FIFO_SIZE       (256)
#define FIFO_ALARM      (191)
#define FIFO_HALF       (FIFO_SIZE / 2)
#define RBUF_M_RX_CHAR      (0377)
#define RBUF_M_RX_LINE      (07)
#define RBUF_V_RX_LINE      (8)
#define RBUF_PARITY_ERR     (1 << 12)
#define RBUF_FRAME_ERR      (1 << 13)
#define RBUF_OVERRUN_ERR    (1 << 14)
#define RBUF_DATA_VALID     (1 << 15)
#define RBUF_GETLINE(u,x)     \
        (((x) >> RBUF_V_RX_LINE) & \
         ((vh_unit[(u)].flags & UNIT_MODEDHU) ? 017 : 07))
#define RBUF_PUTLINE(u,x)     \
        (((x) & ((vh_unit[(u)].flags & UNIT_MODEDHU) ? 017 : 07)) << RBUF_V_RX_LINE)
#define RBUF_DIAG       \
    (RBUF_PARITY_ERR|RBUF_FRAME_ERR|RBUF_OVERRUN_ERR)
#define XON         (021)
#define XOFF            (023)

/* Transmit Character Register (TXCHAR) */

#define TXCHAR_M_CHAR       (0377)
#define TXCHAR_TX_DATA_VALID    (1 << 15)

/* Receive Timer Register (RXTIMER) */

#define RXTIMER_M_RX_TIMER  (0377)

/* Line-Parameter Register (LPR) */

#define LPR_DISAB_XRPT      (1 << 0)    /* not impl. in real DHU */
#define LPR_V_DIAG      (1)
#define LPR_M_DIAG      (03)
#define LPR_V_CHAR_LGTH     (3)
#define LPR_M_CHAR_LGTH     (03)
#define LPR_PARITY_ENAB     (1 << 5)
#define LPR_EVEN_PARITY     (1 << 6)
#define LPR_STOP_CODE       (1 << 7)
#define LPR_V_RX_SPEED      (8)
#define LPR_M_RX_SPEED      (017)
#define LPR_V_TX_SPEED      (12)
#define LPR_M_TX_SPEED      (017)

#define RATE_50         (0)
#define RATE_75         (1)
#define RATE_110        (2)
#define RATE_134        (3)
#define RATE_150        (4)
#define RATE_300        (5)
#define RATE_600        (6)
#define RATE_1200       (7)
#define RATE_1800       (8)
#define RATE_2000       (9)
#define RATE_2400       (10)
#define RATE_4800       (11)
#define RATE_7200       (12)
#define RATE_9600       (13)
#define RATE_19200      (14)
#define RATE_38400      (15)

/* Line-Status Register (STAT) */

#define STAT_DHUID      (1 << 8)    /* mode: 0=DHV, 1=DHU */
#define STAT_MDL        (1 << 9)    /* always 0, has modem support */
#define STAT_CTS        (1 << 11)   /* CTS from modem */
#define STAT_DCD        (1 << 12)   /* DCD from modem */
#define STAT_RI         (1 << 13)   /* RI from modem */
#define STAT_DSR        (1 << 15)   /* DSR from modem */

/* FIFO Size Register (FIFOSIZE) */

#define FIFOSIZE_M_SIZE     (0377)

/* FIFO Data Register (FIFODATA) */

#define FIFODATA_W0     (0377)
#define FIFODATA_V_W1       (8)
#define FIFODATA_M_W1       (0377)

/* Line-Control Register (LNCTRL) */

#define LNCTRL_TX_ABORT     (1 << 0)
#define LNCTRL_IAUTO        (1 << 1)
#define LNCTRL_RX_ENA       (1 << 2)
#define LNCTRL_BREAK        (1 << 3)
#define LNCTRL_OAUTO        (1 << 4)
#define LNCTRL_FORCE_XOFF   (1 << 5)
#define LNCTRL_V_MAINT      (6)
#define LNCTRL_M_MAINT      (03)
#define LNCTRL_LINK_TYPE    (1 << 8)    /* 0=data leads only, 1=modem */
#define LNCTRL_DTR      (1 << 9)    /* DTR to modem */
#define LNCTRL_RTS      (1 << 12)   /* RTS to modem */

/* Transmit Buffer Address Register Number 1 (TBUFFAD1) */

/* Transmit Buffer Address Register Number 2 (TBUFFAD2) */

#define TB2_M_TBUFFAD       (077)
#define TB2_TX_DMA_START    (1 << 7)
#define TB2_TX_ENA      (1 << 15)

/* Transmit DMA Buffer Counter (TBUFFCT) */

/* Self-Test Error Codes */

#define SELF_NULL       (0201)
#define SELF_SKIP       (0203)
#define SELF_OCT        (0211)
#define SELF_RAM        (0225)
#define SELF_RCD        (0231)
#define SELF_DRD        (0235)

#define BMP_OK          (0305)
#define BMP_BAD         (0307)

/* Loopback types */

#define LOOP_NONE       (0)
#define LOOP_H325       (1)
#define LOOP_H3101      (2) /* p.2-13 DHQ manual */
/* Local storage */

static uint16   vh_csr[VH_MUXES]    = { 0 };    /* CSRs */
static uint16   vh_timer[VH_MUXES]  = { 1 };    /* controller timeout */
static uint16   vh_mcount[VH_MUXES] = { 0 };
static uint32   vh_timeo[VH_MUXES]  = { 0 };
static uint32   vh_ovrrun[VH_MUXES] = { 0 };    /* line overrun bits */
/* XOFF'd channels, one bit/channel */
static uint32   vh_stall[VH_MUXES]  = { 0 };
static uint16   vh_loop[VH_MUXES]   = { 0 };    /* loopback status */

/* One bit per controller: */
static uint32   vh_rxi = 0; /* rcv interrupts */
static uint32   vh_txi = 0; /* xmt interrupts */
static uint32   vh_crit = 0;    /* FIFO.CRIT */

static const int32 bitmask[4] = { 037, 077, 0177, 0377 };

/* RX FIFO state */

static int32    rbuf_idx[VH_MUXES]      = { 0 };/* index into vh_rbuf */
static uint32   vh_rbuf[VH_MUXES][FIFO_SIZE]    = { { 0 } };

/* TXQ state */

#define TXQ_SIZE    (16)
static int32    txq_idx[VH_MUXES]       = { 0 };
static uint32   vh_txq[VH_MUXES][TXQ_SIZE]  = { { 0 } };

/* Need to extend the TMLN structure */

typedef struct {
    TMLN    *tmln;
    uint16  lpr;        /* line parameters */
    uint16  lnctrl;     /* line control */
    uint16  lstat;      /* line modem status */
    uint16  tbuffct;    /* remaining character count */
    uint16  tbuf1;
    uint16  tbuf2;
    uint16  txchar;     /* single character I/O */
} TMLX;

static TMLN vh_ldsc[VH_MUXES * VH_LINES_ALLOC] = { { 0 } };
static TMXR vh_desc = { VH_MUXES * VH_LINES_ALLOC, 0, 0, vh_ldsc };
static TMLX vh_parm[VH_MUXES * VH_LINES_ALLOC] = { { 0 } };

/* debugging bitmaps */
#define DBG_REG  0x0001                                 /* trace read/write registers */
#define DBG_INT  0x0002                                 /* display transfer requests */
// #define DBG_XMT  TMXR_DBG_XMT                           /* display Transmitted Data */
// #define DBG_RCV  TMXR_DBG_RCV                           /* display Received Data */

DEBTAB vh_debug[] = {
  {"REG",    DBG_REG},
  {"INT",    DBG_INT},
//  {"XMT",    DBG_XMT},
//  {"RCV",    DBG_RCV},
  {0}
};

/* Forward references */
static t_stat vh_rd (int32 *data, int32 PA, int32 access);
static t_stat vh_wr (int32 data, int32 PA, int32 access);
static t_stat vh_svc (UNIT *uptr);
static int32 vh_rxinta (void);
static int32 vh_txinta (void);
static t_stat vh_clear (int32 vh, t_bool flag);
static t_stat vh_reset (DEVICE *dptr);
static t_stat vh_attach (UNIT *uptr, char *cptr);
static t_stat vh_detach (UNIT *uptr);       
static t_stat vh_show_detail (FILE *st, UNIT *uptr, int32 val, void *desc);
static t_stat vh_show_rbuf (FILE *st, UNIT *uptr, int32 val, void *desc);
static t_stat vh_show_txq (FILE *st, UNIT *uptr, int32 val, void *desc);
static t_stat vh_putc (int32 vh, TMLX *lp, int32 chan, int32 data);
static void doDMA (int32 vh, int32 chan);
static t_stat vh_setnl (UNIT *uptr, int32 val, char *cptr, void *desc);
static t_stat vh_set_log (UNIT *uptr, int32 val, char *cptr, void *desc);
static t_stat vh_set_nolog (UNIT *uptr, int32 val, char *cptr, void *desc);
static t_stat vh_show_log (FILE *st, UNIT *uptr, int32 val, void *desc);

/* SIMH I/O Structures */

static DIB vh_dib = {
    IOBA_VH,
    IOLN_VH * VH_MUXES,
    &vh_rd,     /* read */
    &vh_wr,     /* write */
    2,          /* # of vectors */
    IVCL (VHRX),
    VEC_VHRX,
    { &vh_rxinta, &vh_txinta }  /* int. ack. routines */
};

static UNIT vh_unit[VH_MUXES] = {
    { UDATA (&vh_svc, UNIT_IDLE|UNIT_ATTABLE, 0) },
};

static const REG vh_reg[] = {
    { BRDATA (CSR,     vh_csr, DEV_RDX, 16, VH_MUXES) },
    { GRDATA (DEVADDR, vh_dib.ba, DEV_RDX, 32, 0), REG_HRO },
    { GRDATA (DEVVEC,  vh_dib.vec, DEV_RDX, 16, 0), REG_HRO },
    { NULL }
};

static const MTAB vh_mod[] = {
    { UNIT_MODEDHU, 0, "DHV mode", "DHV", NULL },
    { UNIT_MODEDHU, UNIT_MODEDHU, "DHU mode", "DHU", NULL },
    { UNIT_FASTDMA, 0, NULL, "NORMAL", NULL },
    { UNIT_FASTDMA, UNIT_FASTDMA, "fast DMA", "FASTDMA", NULL },
    { UNIT_MODEM, 0, NULL, "NOMODEM", NULL },
    { UNIT_MODEM, UNIT_MODEM, "modem", "MODEM", NULL },
    { UNIT_HANGUP, 0, NULL, "NOHANGUP", NULL },
    { UNIT_HANGUP, UNIT_HANGUP, "hangup", "HANGUP", NULL },
    { MTAB_XTD|MTAB_VDV, 020, "ADDRESS", "ADDRESS",
        &set_addr, &show_addr, NULL },
    { MTAB_XTD|MTAB_VDV, 8, "VECTOR", "VECTOR",
        &set_vec, &show_vec_mux, (void *) &vh_desc },
    { MTAB_XTD|MTAB_VDV, 0, NULL, "AUTOCONFIGURE",
        &set_addr_flt, NULL, NULL },
    { MTAB_XTD|MTAB_VDV, 0, "LINES", "LINES",
        &vh_setnl, &tmxr_show_lines, (void *) &vh_desc },
    { UNIT_ATT, UNIT_ATT, "summary", NULL,
        NULL, &tmxr_show_summ, (void *) &vh_desc },
    { MTAB_XTD|MTAB_VDV | MTAB_NMO, 1, "CONNECTIONS", NULL,
        NULL, &tmxr_show_cstat, (void *) &vh_desc },
    { MTAB_XTD|MTAB_VDV | MTAB_NMO, 0, "STATISTICS", NULL,
        NULL, &tmxr_show_cstat, (void *) &vh_desc },
    { MTAB_XTD|MTAB_VDV, 1, NULL, "DISCONNECT",
        &tmxr_dscln, NULL, &vh_desc },
    { MTAB_XTD|MTAB_VDV | MTAB_NMO, 0, "DETAIL", NULL,
        NULL, &vh_show_detail, NULL },
    { MTAB_XTD|MTAB_VDV | MTAB_NMO, 0, "RBUF", NULL,
        NULL, &vh_show_rbuf, NULL },
    { MTAB_XTD|MTAB_VDV | MTAB_NMO, 0, "TXQ", NULL,
        NULL, &vh_show_txq, NULL },
    { MTAB_XTD|MTAB_VDV | MTAB_NC, 0, NULL, "LOG",
      &vh_set_log, NULL, &vh_desc },
    { MTAB_XTD|MTAB_VDV | MTAB_NC, 0, NULL, "NOLOG",
      &vh_set_nolog, NULL, &vh_desc },
    { MTAB_XTD|MTAB_VDV | MTAB_NMO, 0, "LOG", NULL,
      NULL, &vh_show_log, &vh_desc },
    { 0 }
};

DEVICE vh_dev = {
    "VH",           /* name */
    vh_unit,        /* units */
    (REG *)vh_reg,  /* registers */
    (MTAB *)vh_mod, /* modifiers */
    VH_MUXES,       /* # units */
    DEV_RDX,        /* address radix */
    8,              /* address width */
    1,              /* address increment */
    DEV_RDX,        /* data radix */
    8,              /* data width */
    NULL,           /* examine routine */
    NULL,           /* deposit routine */
    &vh_reset,      /* reset routine */
    NULL,           /* boot routine */
    &vh_attach,     /* attach routine */
    &vh_detach,     /* detach routine */
    (void *)&vh_dib,/* context */
    DEV_FLTA | DEV_DISABLE | DEV_DIS |DEV_NET | DEV_QBUS | DEV_UBUS | DEV_DEBUG,    /* flags */
    0, vh_debug
};

/* Register names for Debug tracing */
static char *vh_rd_dhv_regs[] =
    {"CSR   ", "RBUF  ", "LPR   ", "STAT  ", "LNCTRL", "TBFAD1", "TBFAD2", "TBFCNT" };
static char *vh_wr_dhv_regs[] =
    {"CSR   ", "TXCHAR", "LPR   ", "STAT  ", "LNCTRL", "TBFAD1", "TBFAD2", "TBFCNT" };
static char *vh_rd_dhu_regs[] =
    {"CSR   ", "RBUF  ", "LPR   ", "FIFOSZ", "LNCTRL", "TBFAD1", "TBFAD2", "TBFCNT" };
static char *vh_wr_dhu_regs[] =
    {"CSR   ", "RXTIMR", "LPR   ", "FIFODT", "LNCTRL", "TBFAD1", "TBFAD2", "TBFCNT" };

/* Interrupt routines */

static void vh_clr_rxint (  int32   vh  )
{
    vh_rxi &= ~(1 << vh);
    if (vh_rxi == 0)
        CLR_INT (VHRX);
    else
        SET_INT (VHRX);
}

static void vh_set_rxint (  int32   vh  )
{
    vh_rxi |= (1 << vh);
    SET_INT (VHRX);
}

/* RX interrupt ack. (bus cycle) */

static int32 vh_rxinta (void)
{
    int32   vh;

    for (vh = 0; vh < vh_desc.lines/VH_LINES; vh++) {
        if (vh_rxi & (1 << vh)) {
            sim_debug(DBG_INT, &vh_dev, "vh_rzinta(vh=%d)\n", vh);
            vh_clr_rxint (vh);
            return (vh_dib.vec + (vh * 010));
        }
    }
    return (0);
}

static void vh_clr_txint (  int32   vh  )
{
    vh_txi &= ~(1 << vh);
    if (vh_txi == 0)
        CLR_INT (VHTX);
    else
        SET_INT (VHTX);
}

static void vh_set_txint (  int32   vh  )
{
    vh_txi |= (1 << vh);
    SET_INT (VHTX);
}

/* TX interrupt ack. (bus cycle) */

static int32 vh_txinta (void)
{
    int32   vh;

    for (vh = 0; vh < vh_desc.lines/VH_LINES; vh++) {
        if (vh_txi & (1 << vh)) {
            sim_debug(DBG_INT, &vh_dev, "vh_txinta(vh=%d)\n", vh);
            vh_clr_txint (vh);
            return (vh_dib.vec + 4 + (vh * 010));
        }
    }
    return (0);
}
/* RX FIFO get/put routines */

/* return 0 on success, -1 on FIFO overflow */

static int32 fifo_put ( int32   vh,
            TMLX    *lp,
            int32   data    )
{
    int32   status = 0;

    if (lp == NULL)
        goto override;
    /* this might have to move to vh_getc() */
    if ((lp->lnctrl & LNCTRL_OAUTO) && ((data & RBUF_DIAG) == 0)) {
        TMLX    *l0p;
        /* implement transmitted data flow control */
        switch (data & 0377) {
        case XON:
            lp->tbuf2 |= TB2_TX_ENA;
            goto common;
        case XOFF:
            lp->tbuf2 &= ~TB2_TX_ENA;
        common:
            /* find line 0 for this controller */
            l0p = &vh_parm[vh * VH_LINES];
            if (l0p->lpr & LPR_DISAB_XRPT)
                return (0);
            break;
        default:
            break;
        }
    }
/* BUG: which of the following 2 is correct? */
    /* if ((data & RBUF_DIAG) == RBUF_DIAG) */
    if (data & RBUF_DIAG)
        goto override;
    if (((lp->lnctrl >> LNCTRL_V_MAINT) & LNCTRL_M_MAINT) == 2)
        goto override;
    if (!(lp->lnctrl & LNCTRL_RX_ENA))
        return (0); 
override:
    vh_csr[vh] |= CSR_RX_DATA_AVAIL;
    if (rbuf_idx[vh] < FIFO_SIZE) {
        vh_rbuf[vh][rbuf_idx[vh]] = data;
        rbuf_idx[vh] += 1;
    } else {
        vh_ovrrun[vh] |= (1 << RBUF_GETLINE (vh, data));
        status = -1;
    }
    if (vh_csr[vh] & CSR_RXIE) {
        if (vh_unit[vh].flags & UNIT_MODEDHU) {
            /* was it a modem status change? */
            if ((data & RBUF_DIAG) == RBUF_DIAG)
                vh_set_rxint (vh);
            /* look for FIFO alarm @ 3/4 full */
            else if (rbuf_idx[vh] == FIFO_ALARM)
                vh_set_rxint (vh);
            else if (vh_timer[vh] == 0)
                ; /* nothing, infinite timeout */
            else if (vh_timer[vh] == 1)
                vh_set_rxint (vh);
            else if (vh_timeo[vh] == 0)
                vh_timeo[vh] = MS2SIMH (vh_timer[vh]) + 1;
        } else {
            /* Interrupt on transition _from_ an empty FIFO */
            if (rbuf_idx[vh] == 1)
                vh_set_rxint (vh);
        }
    }
    if (rbuf_idx[vh] > FIFO_ALARM)
        vh_crit |= (1 << vh);
    /* Implement RX FIFO-level flow control */
    if (lp != NULL) {
        if ((lp->lnctrl & LNCTRL_FORCE_XOFF) || 
              ((vh_crit & (1 << vh)) && (lp->lnctrl & LNCTRL_IAUTO))) {
            int32   chan = RBUF_GETLINE(vh, data);
            vh_stall[vh] ^= (1 << chan);
            /* send XOFF every other character received */
            if (vh_stall[vh] & (1 << chan))
                vh_putc (vh, lp, chan, XOFF);
        }
    }
    return (status);
}

static int32 fifo_get ( int32   vh  )
{
    int32   data, i;

    if (rbuf_idx[vh] == 0)
        return (0);

    /* pick off the first character, mark valid */
    data = vh_rbuf[vh][0] | RBUF_DATA_VALID;
    /* move the remainder up */
    rbuf_idx[vh] -= 1;
    for (i = 0; i < rbuf_idx[vh]; i++)
        vh_rbuf[vh][i] = vh_rbuf[vh][i + 1];
    /* rbuf_idx[vh] -= 1; */
    /* look for any previous overruns */
    if (vh_ovrrun[vh]) {
        for (i = 0; i < VH_LINES; i++) {
            if (vh_ovrrun[vh] & (1 << i)) {
                fifo_put (vh, NULL, RBUF_OVERRUN_ERR |
                      RBUF_PUTLINE (vh, i));
                vh_ovrrun[vh] &= ~(1 << i);
                break;
            }
        }
    }
    /* recompute FIFO alarm condition */
    if ((rbuf_idx[vh] < FIFO_HALF) && (vh_crit & (1 << vh))) {
        vh_crit &= ~(1 << vh);
        /* send XON to all XOFF'd channels on this controller */
        for (i = 0; i < VH_LINES; i++) {
            TMLX    *lp = &vh_parm[(vh * VH_LINES) + i];
            if (lp->lnctrl & LNCTRL_FORCE_XOFF)
                continue;
            if (vh_stall[vh] & (1 << i)) {
                vh_putc (vh, NULL, i, XON);
                vh_stall[vh] &= ~(1 << i);
            }
        }
    }

    if (rbuf_idx[vh] == 0)                  /* FIFO just became empty? */
        vh_csr[vh] &= ~CSR_RX_DATA_AVAIL;   /* clear CSR bit to indicate this */

    return (data & 0177777);
}
/* TX Q manipulation */

static int32 dq_tx_report ( int32   vh  )
{
    int32   data, i;

    if (txq_idx[vh] == 0)
        return (0);
    data = vh_txq[vh][0];
    txq_idx[vh] -= 1;
    for (i = 0; i < txq_idx[vh]; i++)
        vh_txq[vh][i] = vh_txq[vh][i + 1];
    /* txq_idx[vh] -= 1; */
    return (data & 0177777);
}

static void q_tx_report (   int32   vh,
                int32   data    )
{
    if (vh_csr[vh] & CSR_TXIE)
        vh_set_txint (vh);
    if (txq_idx[vh] >= TXQ_SIZE) {
/* BUG: which of the following 2 is correct? */
        dq_tx_report (vh);
        /* return; */
    }
    vh_txq[vh][txq_idx[vh]] = CSR_TX_ACTION | data;
    txq_idx[vh] += 1;
}
/* Channel get/put routines */

static void HangupModem (   int32   vh,
                TMLX    *lp,
                int32   chan    )
{
    if (vh_unit[vh].flags & UNIT_MODEM)
        lp->lstat &= ~(STAT_DCD|STAT_DSR|STAT_CTS|STAT_RI);
    if (lp->lnctrl & LNCTRL_LINK_TYPE)
        /* RBUF<0> = 0 for modem status */
        fifo_put (vh, lp, RBUF_DIAG |
                  RBUF_PUTLINE (vh, chan) |
                  ((lp->lstat >> 8) & 0376));
        /* BUG: check for overflow above */
}

/* TX a character on a line, regardless of the TX enable state */

static t_stat vh_putc ( int32   vh,
            TMLX    *lp,
            int32   chan,
            int32   data    )
{
    int32   val;
    t_stat  status = SCPE_OK;

    /* truncate to desired character length */
    data &= bitmask[(lp->lpr >> LPR_V_CHAR_LGTH) & LPR_M_CHAR_LGTH];
    switch ((lp->lnctrl >> LNCTRL_V_MAINT) & LNCTRL_M_MAINT) {
    case 0:     /* normal */
#if 0
        /* check for (external) loopback setting */
        switch (vh_loop[vh]) {
        default:
        case LOOP_NONE:
            break;
        }
#endif
        status = tmxr_putc_ln (lp->tmln, data);
        if (status == SCPE_LOST) {
            tmxr_reset_ln (lp->tmln);
            HangupModem (vh, lp, chan);
        } else if (status == SCPE_STALL) {
            /* let's flush and try again */
            tmxr_send_buffered_data (lp->tmln);
            status = tmxr_putc_ln (lp->tmln, data);
        }
        break;
    case 1:     /* auto echo */
        break;
    case 2:     /* local loopback */
        if (lp->lnctrl & LNCTRL_BREAK)
            val = fifo_put (vh, lp,
                RBUF_FRAME_ERR | RBUF_PUTLINE (vh, chan));
        else
            val = fifo_put (vh, lp,
                RBUF_PUTLINE (vh, chan) | data);
        status = (val < 0) ? SCPE_TTMO : SCPE_OK;
        break;
    default:    /* remote loopback */
        break;
    }
    return (status);
}

/* Retrieve all stored input from TMXR and place in RX FIFO */

static void vh_getc (   int32   vh  )
{
    uint32  i, c;
    TMLX    *lp;

    for (i = 0; i < (uint32)VH_LINES; i++) {
        lp = &vh_parm[(vh * VH_LINES) + i];
        while ((c = tmxr_getc_ln (lp->tmln)) != 0) {
            if (c & SCPE_BREAK) {
                fifo_put (vh, lp,
                    RBUF_FRAME_ERR | RBUF_PUTLINE (vh, i));
                /* BUG: check for overflow above */
            } else {
                c &= bitmask[(lp->lpr >> LPR_V_CHAR_LGTH) &
                    LPR_M_CHAR_LGTH];
                fifo_put (vh, lp, RBUF_PUTLINE (vh, i) | c);
                /* BUG: check for overflow above */
            }
        }
    }
}

/* I/O dispatch routines */

static t_stat vh_rd (   int32   *data,
            int32   PA,
            int32   access  )
{
    int32   vh = ((PA - vh_dib.ba) >> 4) & VH_MNOMASK, line;
    TMLX    *lp;

    switch ((PA >> 1) & 7) {
    case 0:     /* CSR */
        *data = vh_csr[vh] | dq_tx_report (vh);
        vh_csr[vh] &= ~0117400; /* clear the read-once bits */
        break;
    case 1:     /* RBUF */
        *data = fifo_get (vh);
        break;
    case 2:     /* LPR */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES) {
            *data = 0;
            break;
        }
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        *data = lp->lpr;
        break;
    case 3:     /* STAT/FIFOSIZE */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES) {
            *data = 0;
            break;
        }
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        *data = (lp->lstat & ~0377) |       /* modem status */
#if 0
            (64 - tmxr_tqln (lp->tmln));
fprintf (stderr, "\rtqln %d\n", 64 - tmxr_tqln (lp->tmln));
#else
            64;
#endif
        break;
    case 4:     /* LNCTRL */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES) {
            *data = 0;
            break;
        }
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        *data = lp->lnctrl;
        break;
    case 5:     /* TBUFFAD1 */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES) {
            *data = 0;
            break;
        }
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        *data = lp->tbuf1;
        break;
    case 6:     /* TBUFFAD2 */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES) {
            *data = 0;
            break;
        }
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        *data = lp->tbuf2;
        break;
    case 7:     /* TBUFFCT */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES) {
            *data = 0;
            break;
        }
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        *data = lp->tbuffct;
        break;
    default:
        /* can't happen */
        break;
    }

    sim_debug(DBG_REG, &vh_dev, "vh_rd(PA=0x%08X [%s], access=%d, data=0x%X)\n", PA, 
              ((vh_unit[vh].flags & UNIT_MODEDHU) ? vh_rd_dhu_regs : vh_rd_dhv_regs)[(PA >> 1) & 07], access, data);

    return (SCPE_OK);
}

static t_stat vh_wr (   int32   data,
            int32   PA,
            int32   access  )
{
    int32   vh = ((PA - vh_dib.ba) >> 4) & VH_MNOMASK, line;
    TMLX    *lp;

    sim_debug(DBG_REG, &vh_dev, "vh_wr(PA=0x%08X [%s], access=%d, data=0x%X)\n", PA, 
              ((vh_unit[vh].flags & UNIT_MODEDHU) ? vh_wr_dhu_regs : vh_wr_dhv_regs)[(PA >> 1) & 07], access, data);

    switch ((PA >> 1) & 7) {   
    case 0:     /* CSR, but no read-modify-write */
        if (access == WRITEB)
            data = (PA & 1) ?
                (vh_csr[vh] & 0377) | (data << 8) :
                (vh_csr[vh] & ~0377) | (data & 0377);
        if (data & CSR_MASTER_RESET) {
            if ((vh_unit[vh].flags & UNIT_MODEDHU) && (data & CSR_SKIP))
                data &= ~CSR_MASTER_RESET;
            if (vh == 0) /* Only start unit service on the first unit.  Units are polled there */
                sim_activate (&vh_unit[vh], clk_cosched (tmxr_poll));
            /* vh_mcount[vh] = 72; */ /* 1.2 seconds */
            vh_mcount[vh] = MS2SIMH (1200); /* 1.2 seconds */
        }
        if ((data & CSR_RXIE) == 0)
            vh_clr_rxint (vh);
        /* catch the RXIE transition if the FIFO is not empty */
        else if (((vh_csr[vh] & CSR_RXIE) == 0) &&
              (rbuf_idx[vh] != 0)) {
            if (vh_unit[vh].flags & UNIT_MODEDHU) {
                if (rbuf_idx[vh] > FIFO_ALARM)
                    vh_set_rxint (vh);
                else if (vh_timer[vh] == 0)
                    ;
                else if (vh_timer[vh] == 1)
                    vh_set_rxint (vh);
                else if (vh_timeo[vh] == 0)
                    vh_timeo[vh] = MS2SIMH (vh_timer[vh]) + 1;
            } else {
                vh_set_rxint (vh);
            }
        }
        if ((data & CSR_TXIE) == 0)
            vh_clr_txint (vh);
        else if (((vh_csr[vh] & CSR_TXIE) == 0) &&
              (txq_idx[vh] != 0))
            vh_set_txint (vh);
        vh_csr[vh] = (vh_csr[vh] & ~((uint16) CSR_RW)) | (data & (uint16) CSR_RW);
        break;
    case 1:     /* TXCHAR/RXTIMER */
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)
            break;
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (vh_unit[vh].flags & UNIT_MODEDHU) {
            if (CSR_GETCHAN (vh_csr[vh]) != 0)
                break;
            if (access == WRITEB)
                data = (PA & 1) ?
                    (vh_timer[vh] & 0377) | (data << 8) :
                    (vh_timer[vh] & ~0377) | (data & 0377);
            vh_timer[vh] = data & 0377;
#if 0
            if (vh_csr[vh] & CSR_RXIE) {
                if (rbuf_idx[vh] > FIFO_ALARM)
                    vh_set_rxint (vh);
                else if (vh_timer[vh] == 0)
                    ;
                else if (vh_timer[vh] == 1)
                    vh_set_rxint (vh);
                else if (vh_timeo[vh] == 0)
                    vh_timeo[vh] = MS2SIMH (vh_timer[vh]) + 1;
            }
#endif
        } else {
            line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
            lp = &vh_parm[line];
            if (access == WRITEB)
                data = (PA & 1) ?   
                    (lp->txchar & 0377) | (data << 8) :
                    (lp->txchar & ~0377) | (data & 0377);
            lp->txchar = data;  /* TXCHAR */
            if (lp->txchar & TXCHAR_TX_DATA_VALID) {
                if (lp->tbuf2 & TB2_TX_ENA)
                    vh_putc (vh, lp,
                        CSR_GETCHAN (vh_csr[vh]),
                        lp->txchar);
                q_tx_report (vh,
                    CSR_GETCHAN (vh_csr[vh]) << CSR_V_TX_LINE);
                lp->txchar &= ~TXCHAR_TX_DATA_VALID;
            }
        }
        break;
    case 2:     /* LPR */
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)
            break;
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        if (access == WRITEB)
            data = (PA & 1) ?
                (lp->lpr & 0377) | (data << 8) :
                (lp->lpr & ~0377) | (data & 0377);
        /* Modify only if CSR<3:0> == 0 */
        if (CSR_GETCHAN (vh_csr[vh]) != 0)
            data &= ~LPR_DISAB_XRPT;
        lp->lpr = data;
        if (((lp->lpr >> LPR_V_DIAG) & LPR_M_DIAG) == 1) {
            fifo_put (vh, lp,
                RBUF_DIAG |
                RBUF_PUTLINE (vh, CSR_GETCHAN (vh_csr[vh])) |
                BMP_OK);
            /* BUG: check for overflow above */
            lp->lpr &= ~(LPR_M_DIAG << LPR_V_DIAG);
        }
        break;
    case 3:     /* STAT/FIFODATA */
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)
            break;
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        if (vh_unit[vh].flags & UNIT_MODEDHU) {
            /* high byte writes not allowed */
            if (PA & 1)
                break;
            /* transmit 1 or 2 characters */
            if (!(lp->tbuf2 & TB2_TX_ENA))
                break;
            vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]), data);
            q_tx_report (vh, CSR_GETCHAN (vh_csr[vh]) << CSR_V_TX_LINE);
            if (access != WRITEB)
                vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]),
                    data >> 8);
        }
        break;
    case 4:     /* LNCTRL */
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)   
            break;
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        if (access == WRITEB)
            data = (PA & 1) ?
                (lp->lnctrl & 0377) | (data << 8) :
                (lp->lnctrl & ~0377) | (data & 0377);
        /* catch the abort TX transition */
        if (!(lp->lnctrl & LNCTRL_TX_ABORT) &&
             (data & LNCTRL_TX_ABORT)) {
            if ((lp->tbuf2 & TB2_TX_ENA) &&
                (lp->tbuf2 & TB2_TX_DMA_START)) {
                lp->tbuf2 &= ~TB2_TX_DMA_START;
                q_tx_report (vh, CSR_GETCHAN (vh_csr[vh]) << CSR_V_TX_LINE);
            }
        }
        /* Implement program-initiated flow control */
        if ( (data & LNCTRL_FORCE_XOFF) &&
             !(lp->lnctrl & LNCTRL_FORCE_XOFF) ) {
            if (!(lp->lnctrl & LNCTRL_IAUTO))
                vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]), XOFF);
        } else if ( !(data & LNCTRL_FORCE_XOFF) &&
                (lp->lnctrl & LNCTRL_FORCE_XOFF) ) {
            if (!(lp->lnctrl & LNCTRL_IAUTO))
                vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]), XON);
            else if (!(vh_crit & (1 << vh)) &&
                 (vh_stall[vh] & (1 << CSR_GETCHAN (vh_csr[vh]))))
                vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]), XON);
        }
        if ( (data & LNCTRL_IAUTO) &&       /* IAUTO 0->1 */
             !(lp->lnctrl & LNCTRL_IAUTO) ) {
            if (!(lp->lnctrl & LNCTRL_FORCE_XOFF)) {
                if (vh_crit & (1 << vh)) {
                    vh_putc (vh, lp,
                        CSR_GETCHAN (vh_csr[vh]), XOFF);
                    vh_stall[vh] |= (1 << CSR_GETCHAN (vh_csr[vh]));
                }
            } else {
                /* vh_stall[vh] |= (1 << CSR_GETCHAN (vh_csr[vh])) */;
            }
        } else if ( !(data & LNCTRL_IAUTO) &&
                (lp->lnctrl & LNCTRL_IAUTO) ) {
            if (!(lp->lnctrl & LNCTRL_FORCE_XOFF))
                vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]), XON);
        }
        /* check modem control bits */
        if ( !(data & LNCTRL_DTR) &&    /* DTR 1->0 */
              (lp->lnctrl & LNCTRL_DTR)) {
            if ((lp->tmln->conn) && (vh_unit[vh].flags & UNIT_HANGUP)) {
                tmxr_linemsg (lp->tmln, "\r\nLine hangup\r\n");
                tmxr_reset_ln (lp->tmln);
            }
            HangupModem (vh, lp, CSR_GETCHAN (vh_csr[vh]));
        }
        lp->lnctrl = data;
        lp->tmln->rcve = (data & LNCTRL_RX_ENA) ? 1 : 0;
        tmxr_poll_rx (&vh_desc);
        vh_getc (vh);
        if (lp->lnctrl & LNCTRL_BREAK)
            vh_putc (vh, lp, CSR_GETCHAN (vh_csr[vh]), 0);
        break;
    case 5:     /* TBUFFAD1 */
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)   
            break;
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        if (access == WRITEB)
            data = (PA & 1) ?
                (lp->tbuf1 & 0377) | (data << 8) :
                (lp->tbuf1 & ~0377) | (data & 0377);
        lp->tbuf1 = data;
        break;
    case 6:     /* TBUFFAD2 */
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)
            break;
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        if (access == WRITEB)
            data = (PA & 1) ?
                (lp->tbuf2 & 0377) | (data << 8) :
                (lp->tbuf2 & ~0377) | (data & 0377);
        lp->tbuf2 = data;
        /* if starting a DMA, clear DMA_ERR */
        if (vh_unit[vh].flags & UNIT_FASTDMA) {
            doDMA (vh, CSR_GETCHAN (vh_csr[vh]));
            tmxr_send_buffered_data (lp->tmln);
        }
        break;
    case 7:     /* TBUFFCT */
        if ((data == RESET_ABORT) && (vh_csr[vh] & CSR_MASTER_RESET)) {
            vh_mcount[vh] = 1;
            break;
        }
        if (CSR_GETCHAN (vh_csr[vh]) >= VH_LINES)
            break;
        line = (vh * VH_LINES) + CSR_GETCHAN (vh_csr[vh]);
        lp = &vh_parm[line];
        if (access == WRITEB)
            data = (PA & 1) ?
                (lp->tbuffct & 0377) | (data << 8) :
                (lp->tbuffct & ~0377) | (data & 0377);
        lp->tbuffct = data;
        break;
    default:
        /* can't happen */
        break;
    }
    return (SCPE_OK);
}

static void doDMA ( int32   vh,
            int32   chan    )
{
    int32   line, status;
    uint32  pa;
    TMLX    *lp;

    line = (vh * VH_LINES) + chan;
    lp = &vh_parm[line];
    if ((lp->tbuf2 & TB2_TX_ENA) && (lp->tbuf2 & TB2_TX_DMA_START)) {
/* BUG: should compare against available xmit buffer space */
        pa = lp->tbuf1;
        pa |= (lp->tbuf2 & TB2_M_TBUFFAD) << 16;
        status = chan << CSR_V_TX_LINE;
        while (lp->tbuffct) {
            uint8   buf;
            if (Map_ReadB (pa, 1, &buf)) {
                status |= CSR_TX_DMA_ERR;
                lp->tbuffct = 0;
                break;
            }
            if (vh_putc (vh, lp, chan, buf) != SCPE_OK)
                break;
            /* pa = (pa + 1) & PAMASK; */
            pa = (pa + 1) & ((1 << 22) - 1);
            lp->tbuffct--;
        }
        lp->tbuf1 = pa & 0177777;
        lp->tbuf2 = (lp->tbuf2 & ~TB2_M_TBUFFAD) |
                ((pa >> 16) & TB2_M_TBUFFAD);
        if (lp->tbuffct == 0) {
            lp->tbuf2 &= ~TB2_TX_DMA_START;
            q_tx_report (vh, status);
        }
    }
}

/* Perform many of the functions of PROC2 */

static t_stat vh_svc (  UNIT    *uptr   )
{
    int32   vh, newln, i;

    /* scan all muxes for countdown reset */
    for (vh = 0; vh < vh_desc.lines/VH_LINES; vh++) {
        if (vh_csr[vh] & CSR_MASTER_RESET) {
            if (vh_mcount[vh] != 0)
                vh_mcount[vh] -= 1;
            else
                vh_clear (vh, FALSE);
        }
    }
    /* sample every 10ms for modem changes (new connections) */
    newln = tmxr_poll_conn (&vh_desc);
    if (newln >= 0) {
        TMLX    *lp;
        int32   line;
        vh = newln / VH_LINES;  /* determine which mux */
        line = newln - (vh * VH_LINES);
        lp = &vh_parm[newln];
        lp->lstat |= STAT_DSR | STAT_DCD | STAT_CTS;
        if (!(lp->lnctrl & LNCTRL_DTR))
            lp->lstat |= STAT_RI;
        if (lp->lnctrl & LNCTRL_LINK_TYPE)
            fifo_put (vh, lp, RBUF_DIAG |
                      RBUF_PUTLINE (vh, line) |
                      ((lp->lstat >> 8) & 0376));
            /* BUG: should check for overflow above */
    }
    /* scan all muxes, lines for DMA to complete; start every 3.12ms */
    for (vh = 0; vh < vh_desc.lines/VH_LINES; vh++) {
        for (i = 0; i < VH_LINES; i++)
            doDMA (vh, i);
    }
    /* interrupt driven in a real DHQ */
    tmxr_poll_rx (&vh_desc);
    for (vh = 0; vh < vh_desc.lines/VH_LINES; vh++)
        vh_getc (vh);
    tmxr_poll_tx (&vh_desc);
    /* scan all DHU-mode muxes for RX FIFO timeout */
    for (vh = 0; vh < vh_desc.lines/VH_LINES; vh++) {
        if (vh_unit[vh].flags & UNIT_MODEDHU) {
            if (vh_timeo[vh] && (vh_csr[vh] & CSR_RXIE)) {
                vh_timeo[vh] -= 1;
                if ((vh_timeo[vh] == 0) && rbuf_idx[vh])
                    vh_set_rxint (vh);
            }
        }
    }
    sim_activate (uptr, tmxr_poll); /* requeue ourselves */
    return (SCPE_OK);
}

/* init a channel on a controller */

/* set for:
send/receive 9600
8 data bits
1 stop bit
no parity
parity odd
auto-flow off
RX disabled
TX enabled
no break on line
no loopback
link type set to data-leads only
DTR & RTS off
DMA character counter 0
DMA start address registers 0
TX_DMA_START 0
TX_ABORT 0
auto-flow reports enabled
FIFO size set to 64
*/

static void vh_init_chan (  int32   vh,
                int32   chan    )
{
    int32   line;
    TMLX    *lp;

    line = (vh * VH_LINES) + chan;
    lp = &vh_parm[line];
    lp->lpr = (RATE_9600 << LPR_V_TX_SPEED) |
          (RATE_9600 << LPR_V_RX_SPEED) |
          (03 << LPR_V_CHAR_LGTH);
    lp->lnctrl = 0;
    lp->lstat &= ~(STAT_MDL | STAT_DHUID | STAT_RI);
    if (vh_unit[vh].flags & UNIT_MODEDHU)
        lp->lstat |= STAT_DHUID | 64;
    if (!(vh_unit[vh].flags & UNIT_MODEM))
        lp->lstat |= STAT_DSR | STAT_DCD | STAT_CTS;
    lp->tmln->xmte = 1;
    lp->tmln->rcve = 0;
    lp->tbuffct = 0;
    lp->tbuf1 = 0;
    lp->tbuf2 = TB2_TX_ENA;
    lp->txchar = 0;
}

/* init a controller; flag true if BINIT, false if master.reset */

static t_stat vh_clear (    int32   vh,
                t_bool  flag    )
{
    int32   i;

    txq_idx[vh] = 0;
    rbuf_idx[vh] = 0;
    /* put 8 diag bytes in FIFO: 6 SELF_x, 2 circuit revision codes */
    if (vh_csr[vh] & CSR_SKIP) {
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 0) | SELF_SKIP);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 1) | SELF_SKIP);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 2) | SELF_SKIP);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 3) | SELF_SKIP);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 4) | SELF_SKIP);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 5) | SELF_SKIP);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 6) | 0107);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 7) | 0105);
    } else {
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 0) | SELF_NULL);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 1) | SELF_NULL);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 2) | SELF_NULL);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 3) | SELF_NULL);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 4) | SELF_NULL);
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 5) | SELF_NULL);
        /* PROC2 ver. 1 */
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 6) | 0107);
        /* PROC1 ver. 1 */
        fifo_put (vh, NULL, RBUF_DIAG | RBUF_PUTLINE(vh, 7) | 0105);
   }
    vh_csr[vh] &= ~(CSR_TX_ACTION|CSR_DIAG_FAIL|CSR_MASTER_RESET);
    if (flag)
        vh_csr[vh] &= ~(CSR_TXIE|CSR_RXIE|CSR_SKIP);
    vh_csr[vh] |= CSR_TX_DMA_ERR | (CSR_M_TX_LINE << CSR_V_TX_LINE);
    vh_clr_rxint (vh);
    vh_clr_txint (vh);
    vh_timer[vh] = 1;
    vh_timeo[vh] = 0;
    vh_ovrrun[vh] = 0;
    for (i = 0; i < VH_LINES; i++)
        vh_init_chan (vh, i);
    vh_crit &= ~(1 << vh);
    vh_stall[vh] = 0;
    vh_loop[vh] = LOOP_NONE;
    return (SCPE_OK);
}

/* Reset all controllers.  Used by BINIT and RESET. */

static t_stat vh_reset (    DEVICE  *dptr   )
{
    int32   i, lines, maxlines;

    for (i = 0; i < vh_desc.lines; i++)
        vh_parm[i].tmln = &vh_ldsc[i];

    /* re-establish lines per unit and lower bounds */
    lines = VH_LINES;
    /* enforce multiples; find next if necessary */
    while ((vh_desc.lines % lines) != 0)
        vh_desc.lines++;
    /* establish upper bounds */
    maxlines = lines * VH_MUXES;
    /* enforce bounds */
    if (vh_desc.lines > maxlines)
        vh_desc.lines = maxlines;
    if (vh_desc.lines < lines)
        vh_desc.lines = lines;

    for (i = 0; i < VH_MUXES; i++) {
        if (i < vh_desc.lines/VH_LINES) {
            /* if Unibus, force DHU mode */
            if (UNIBUS)
                vh_unit[i].flags |= UNIT_MODEDHU;
            else
                vh_unit[i].flags &= ~UNIT_MODEDHU;
            vh_unit[i].flags &= ~UNIT_DIS;
            vh_clear (i, TRUE);
        } else {
            vh_unit[i].flags |= UNIT_DIS;
        }
    }
    vh_rxi = vh_txi = 0;
    CLR_INT (VHRX);
    CLR_INT (VHTX);
    sim_cancel (&vh_unit[0]);
    vh_dib.lnt = (vh_desc.lines / lines) * IOLN_VH;      /* set length */
    vh_dev.numunits = vh_desc.lines / lines;
    return auto_config (dptr->name, (dptr->flags & DEV_DIS) ? 0 : vh_desc.lines/lines);
}


static t_stat vh_attach (   UNIT    *uptr,
                char    *cptr   )
{
    if (uptr == &vh_unit[0])
        return (tmxr_attach (&vh_desc, uptr, cptr));
    return (SCPE_NOATT);
}

static t_stat vh_detach (   UNIT    *uptr   )
{
    return (tmxr_detach (&vh_desc, uptr));
}

static void vh_detail_line (    FILE    *st,
                int32   vh,
                int32   chan    )
{
    int32   line;
    TMLX    *lp;

    line = (vh * VH_LINES) + chan;
    lp = &vh_parm[line];
    fprintf (st, "\tline %d\tlpr %06o, lnctrl %06o, lstat %06o\n",
        chan, lp->lpr, lp->lnctrl, lp->lstat);
    fprintf (st, "\t\ttbuffct %06o, tbuf1 %06o, tbuf2 %06o, txchar %06o\n",
        lp->tbuffct, lp->tbuf1, lp->tbuf2, lp->txchar);
    fprintf (st, "\t\ttmln rcve %d xmte %d\n",
        lp->tmln->rcve, lp->tmln->xmte);
}

static t_stat vh_show_detail (   FILE    *st,
                UNIT    *uptr,
                int32   val,
                void    *desc   )
{
    int32   i, j;

    fprintf (st, "VH:\trxi %d, txi %d\n", vh_rxi, vh_txi);
    for (i = 0; i < vh_desc.lines/VH_LINES; i++) {
        fprintf (st, "VH%d:\tmode %s, crit %d\n", i,
            vh_unit[i].flags & UNIT_MODEDHU ? "DHU" : "DHV",
            vh_crit & (1 << i));
        fprintf (st, "\tCSR %06o, mcount %d, rbuf_idx %d, txq_idx %d\n",
            vh_csr[i], vh_mcount[i], rbuf_idx[i], txq_idx[i]);
        for (j = 0; j < VH_LINES; j++)
            vh_detail_line (st, i, j);
    }
    return (SCPE_OK);
}

static t_stat vh_show_rbuf (    FILE    *st,
                UNIT    *uptr,
                int32   val,
                void    *desc   )
{
    int32   i;

    for (i = 0; i < rbuf_idx[0]; i++)
        fprintf (st, "%03d: %06o\n", i, vh_rbuf[0][i]);
    return (SCPE_OK);
}

static t_stat vh_show_txq ( FILE    *st,
                UNIT    *uptr,
                int32   val,
                void    *desc   )
{
    int32   i;

    for (i = 0; i < txq_idx[0]; i++)
        fprintf (st, "%02d: %06o\n\r", i, vh_txq[0][i]);
    return (SCPE_OK);
}

/* SET LINES processor */

static t_stat vh_setnl (UNIT *uptr, int32 val, char *cptr, void *desc)
{
int32 newln, i, t;
t_stat r;

if (cptr == NULL)
    return SCPE_ARG;
newln = (int32) get_uint (cptr, 10, (VH_MUXES * VH_LINES), &r);
if ((r != SCPE_OK) || (newln == vh_desc.lines))
    return r;
if ((newln == 0) || (newln % VH_LINES))
    return SCPE_ARG;
if (newln < vh_desc.lines) {
    for (i = newln, t = 0; i < vh_desc.lines; i++)
        t = t | vh_ldsc[i].conn;
    if (t && !get_yn ("This will disconnect users; proceed [N]?", FALSE))
        return SCPE_OK;
    for (i = newln; i < vh_desc.lines; i++) {
        if (vh_ldsc[i].conn) {
            tmxr_linemsg (&vh_ldsc[i], "\r\nOperator disconnected line\r\n");
            tmxr_reset_ln (&vh_ldsc[i]);                /* reset line */
            }
        if ((i % VH_LINES) == (VH_LINES - 1))
            vh_clear (i / VH_LINES, TRUE);              /* reset mux */
        }
    }
vh_desc.lines = newln;
return vh_reset (&vh_dev);
}

/* SET LOG processor */

static t_stat vh_set_log (UNIT *uptr, int32 val, char *cptr, void *desc)
{
char *tptr;
t_stat r;
int32 ln;

if (cptr == NULL)
    return SCPE_ARG;
tptr = strchr (cptr, '=');
if ((tptr == NULL) || (*tptr == 0))
    return SCPE_ARG;
*tptr++ = 0;
ln = (int32) get_uint (cptr, 10, (VH_MUXES * VH_LINES), &r);
if ((r != SCPE_OK) || (ln >= vh_desc.lines))
    return SCPE_ARG;
return tmxr_set_log (NULL, ln, tptr, desc);
}

/* SET NOLOG processor */

static t_stat vh_set_nolog (UNIT *uptr, int32 val, char *cptr, void *desc)
{
t_stat r;
int32 ln;

if (cptr == NULL)
    return SCPE_ARG;
ln = (int32) get_uint (cptr, 10, (VH_MUXES * VH_LINES), &r);
if ((r != SCPE_OK) || (ln >= vh_desc.lines))
    return SCPE_ARG;
return tmxr_set_nolog (NULL, ln, NULL, desc);
}

/* SHOW LOG processor */

static t_stat vh_show_log (FILE *st, UNIT *uptr, int32 val, void *desc)
{
int32 i;

for (i = 0; i < vh_desc.lines; i++) {
    fprintf (st, "line %d: ", i);
    tmxr_show_log (st, NULL, i, desc);
    fprintf (st, "\n");
    }
return SCPE_OK;
}
