simh.simh/Altair8800/s100_ram.c

/* s100_ram.c: MITS Altair 8800 RAM

   Copyright (c) 2025 Patrick A. Linstruth

   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
   PETER SCHORN 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 Patrick Linstruth shall not
   be used in advertising or otherwise to promote the sale, use or other dealings
   in this Software without prior written authorization from Patrick Linstruth.

   History:
   07-Nov-2025 Initial version

*/

#include "altair8800_defs.h"
#include "s100_bus.h"
#include "s100_ram.h"

static t_stat ram_reset             (DEVICE *dptr);
static t_stat ram_dep               (t_value val, t_addr addr, UNIT *uptr, int32 sw);
static t_stat ram_ex                (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw);
static int32 ram_memio              (const int32 addr, const int32 rw, const int32 data);
static t_stat ram_default_ena       (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
static t_stat ram_default_dis       (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
static t_stat ram_set_memsize       (int32 value);
static t_stat ram_clear_command     (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
static t_stat ram_enable_command    (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
static t_stat ram_randomize_command (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
static t_stat ram_size_command      (UNIT *uptr, int32 value, CONST char *cptr, void *desc);
static void ram_clear               (void);
static void ram_randomize           (void);
static t_stat ram_show_help         (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr);
static const char* ram_description  (DEVICE *dptr);

static void PutBYTE(register uint32 Addr, const register uint32 Value);
static uint32 GetBYTE(register uint32 Addr);

static int32 poc = TRUE; /* Power On Clear */

static int32 M[MAXBANKSIZE];                 /* RAM */
static int32 P[MAXBANKSIZE >> LOG2PAGESIZE]; /* Active pages */
static int32 memsize = MAXBANKSIZE;

static const char* ram_description(DEVICE *dptr) {
    return "Random Access Memory";
}

static UNIT ram_unit = {
    UDATA (NULL, UNIT_FIX | UNIT_BINK | UNIT_RAM_DEFAULT, MAXBANKSIZE)
};

static REG ram_reg[] = {
    { FLDATAD (POC,     poc,       0x01,         "Power on Clear flag"), },
    { NULL }
};

static MTAB ram_mod[] = {
    { UNIT_RAM_VERBOSE,     UNIT_RAM_VERBOSE,   "VERBOSE",      "VERBOSE",      NULL, NULL,
        NULL, "Enable verbose messages"  },
    { UNIT_RAM_VERBOSE,     0,                  "QUIET",        "QUIET",        NULL, NULL,
        NULL, "Disable verbose messages"                },
    { UNIT_RAM_DEFAULT,     UNIT_RAM_DEFAULT,   "DEFAULT",      "DEFAULT",      &ram_default_ena, NULL,
        NULL, "Enable RAM as default memory"    },
    { UNIT_RAM_DEFAULT,     0,                  "NODEFAULT",    "NODEFAULT",    &ram_default_dis, NULL,
        NULL, "Disable RAM as default memory"   },

    { MTAB_XTD | MTAB_VDV | MTAB_VALR,  0,      NULL, "SIZE={1-64}",                     &ram_size_command,
        NULL, NULL, "Sets the RAM size" },
    { MTAB_XTD | MTAB_VDV | MTAB_VALR,  1,      NULL, "ADDRAM={PAGE | START-END | ALL}", &ram_enable_command,
        NULL, NULL, "Enable RAM page(s)" },
    { MTAB_XTD | MTAB_VDV | MTAB_VALR,  0,      NULL, "REMRAM={PAGE | START-END | ALL}", &ram_enable_command,
        NULL, NULL, "Disable RAM page(s)" },
    { MTAB_VDV,             0,                  NULL, "CLEAR",                           &ram_clear_command,
        NULL, NULL, "Sets RAM to 0x00"  },
    { MTAB_VDV,             0,                  NULL, "RANDOM",                          &ram_randomize_command,
        NULL, NULL, "Sets RAM to random values"  },
    { 0 }
};

/* Debug Flags */
static DEBTAB ram_dt[] = {
    { NULL, 0 }
};

DEVICE ram_dev = {
    "RAM",                     /* name */
    &ram_unit,                 /* units */
    ram_reg,                   /* registers */
    ram_mod,                   /* modifiers */
    1,                         /* # units */
    ADDRRADIX,                 /* address radix */
    ADDRWIDTH,                 /* address width */
    1,                         /* addr increment */
    DATARADIX,                 /* data radix */
    DATAWIDTH,                 /* data width */
    &ram_ex,                   /* examine routine */
    &ram_dep,                  /* deposit routine */
    &ram_reset,                /* reset routine */
    NULL,                      /* boot routine */
    NULL,                      /* attach routine */
    NULL,                      /* detach routine */
    NULL,                      /* context */
    (DEV_DISABLE),             /* flags */
    0,                         /* debug control */
    ram_dt,                    /* debug flags */
    NULL,                      /* mem size routine */
    NULL,                      /* logical name */
    &ram_show_help,            /* help */
    NULL,                      /* attach help */
    NULL,                      /* context available to help routines */
    &ram_description           /* device description */
};

static t_stat ram_reset(DEVICE *dptr)
{
    if (dptr->flags & DEV_DIS) {    /* Disable Device */
        s100_bus_remmem(0x0000, MAXBANKSIZE, &ram_memio);
        ram_default_dis(NULL, 0, NULL, NULL);

        poc = TRUE;
    }
    else {
        if (poc) {
            ram_set_memsize(memsize);

            if (ram_unit.flags & UNIT_RAM_DEFAULT) {
                ram_default_ena(NULL, 0, NULL, NULL);
            }

            poc = FALSE;
        }
    }

    return SCPE_OK;
}

/* memory examine */
static t_stat ram_ex(t_value *vptr, t_addr addr, UNIT *uptr, int32 sw) {
    *vptr = GetBYTE(addr & ADDRMASK) & DATAMASK;

    return SCPE_OK;
}

/* memory deposit */
static t_stat ram_dep(t_value val, t_addr addr, UNIT *uptr, int32 sw) {
    PutBYTE(addr & ADDRMASK, val & DATAMASK);
 
    return SCPE_OK;
}

static int32 ram_memio(const int32 addr, const int32 rw, const int32 data)
{
    if (rw == S100_IO_READ) {
        return GetBYTE(addr);
    }

    PutBYTE(addr, data);

    return 0x0ff;
}

static void PutBYTE(register uint32 Addr, const register uint32 Value)
{
    M[Addr & ADDRMASK] = Value & DATAMASK;
}

static uint32 GetBYTE(register uint32 Addr)
{
    return M[Addr & ADDRMASK] & DATAMASK; /* RAM */
}

static t_stat ram_default_ena(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
{
    s100_bus_setmem_dflt(&ram_memio, "RAM"); /* Set RAM as default memory device */

    return SCPE_OK;
}

static t_stat ram_default_dis(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
{
    s100_bus_remmem_dflt(&ram_memio);       /* Remove RAM as default memory device */

    return SCPE_OK;
}

/* set memory to 'size' kilo byte */
static t_stat ram_set_memsize(int32 size) {
    int32 page;

    size <<= KBLOG2;

    if (size < KB) {
        memsize = KB;
    }
    else if (size > MAXBANKSIZE) {
        memsize = MAXBANKSIZE;
    }
    else {
        memsize = size;
    }

    s100_bus_remmem(0x0000, MAXBANKSIZE, &ram_memio);     /* Remove all pages */
    s100_bus_addmem(0x0000, memsize, &ram_memio, "RAM");  /* Add memsize pages */

    /* Keep track of active pages for SHOW */
    for (page = 0; page < (MAXBANKSIZE >> LOG2PAGESIZE); page++) {
        P[page] = (page << LOG2PAGESIZE) <= memsize;
    }

    ram_unit.capac = memsize;

    return SCPE_OK;
}

static void ram_clear()
{
    uint32 i;

    for (i = 0; i < MAXBANKSIZE; i++) {
        M[i] = 0;
    }
}

static void ram_randomize()
{
    uint32 i;

    for (i = 0; i < MAXBANKSIZE; i++) {
        M[i] = sim_rand() & DATAMASK;
    }
}

static t_stat ram_size_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc) {
    int32 size, result;

    if (cptr == NULL) {
        sim_printf("Memory size must be provided as SET RAM SIZE=1-64\n");
        return SCPE_ARG | SCPE_NOMESSAGE;
    }

    result = sscanf(cptr, "%i", &size);

    if (result == 1) {
        return ram_set_memsize(size); /* Set size in KB */
    }

    return SCPE_ARG | SCPE_NOMESSAGE;
}

static t_stat ram_enable_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc) {
    int32 size;
    t_addr start, end;

    if (cptr == NULL) {
        sim_printf("Memory page(s) must be provided as SET RAM ENABLE=E0-EF\n");
        return SCPE_ARG | SCPE_NOMESSAGE;
    }

    if (get_range(NULL, cptr, &start, &end, 16, PAGEMASK, 0) == NULL) {
        return SCPE_ARG;
    }

    if (start < MAXPAGE) {
        start = start << LOG2PAGESIZE;
    }
    if (end < MAXPAGE) {
        end = end << LOG2PAGESIZE;
    }

    start &= 0xff00;
    end &= 0xff00;

    size = end - start + PAGESIZE;

    if (value) {
        s100_bus_addmem(start, size, &ram_memio, "RAM");  /* Add pages */
    }
    else {
        s100_bus_remmem(start, size, &ram_memio);         /* Remove pages */
    }

    return SCPE_OK;
}

static t_stat ram_clear_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
{
    ram_clear();

    return SCPE_OK;
}

static t_stat ram_randomize_command(UNIT *uptr, int32 value, CONST char *cptr, void *desc)
{
    ram_randomize();

    return SCPE_OK;
}

static t_stat ram_show_help(FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, const char *cptr)
{
    fprintf (st, "\nAltair 8800 RAM (%s)\n", dptr->name);

    fprint_set_help (st, dptr);
    fprint_show_help (st, dptr);
    fprint_reg_help (st, dptr);

    return SCPE_OK;
}