i1401_cd.c - emulators/simh - Rivoreo Source Code Repositories

 /* i1401_cd.c: IBM 1402 card reader/punch

    Copyright (c) 1993-2000, 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
    ROBERT M SUPNIK 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 Robert M Supnik shall not
    be used in advertising or otherwise to promote the sale, use or other dealings
    in this Software without prior written authorization from Robert M Supnik.

    cdr		card reader
    cdp		card punch
    stack	stackers (5 units)
 	0	normal
 	1	1
 	2	2/8
 	3	unused
 	4	4

    Cards are represented as ASCII text streams terminated by newlines.
    This allows cards to be created and edited as normal files.
 */

 #include "i1401_defs.h"
 #include <ctype.h>

 extern unsigned char M[];
 extern int32 ind[64], ssa, iochk;
 extern char bcd_to_ascii[64];
 extern char ascii_to_bcd[128];
 int32 s1sel, s2sel, s4sel, s8sel;
 char rbuf[CBUFSIZE];					/* > CDR_WIDTH */
 t_stat cdr_svc (UNIT *uptr);
 t_stat cdr_boot (int32 unitno);
 t_stat cdr_attach (UNIT *uptr, char *cptr);
 t_stat cd_reset (DEVICE *dptr);
 extern t_stat sim_activate (UNIT *uptr, int32 delay);
 extern t_stat sim_cancel (UNIT *uptr);
 extern int32 sim_is_active (UNIT *uptr);

 /* Card reader data structures

    cdr_dev	CDR descriptor
    cdr_unit	CDR unit descriptor
    cdr_reg	CDR register list
 */

 UNIT cdr_unit = {
 	UDATA (&cdr_svc, UNIT_SEQ+UNIT_ATTABLE, 0), 100 };

 REG cdr_reg[] = {
 	{ FLDATA (LAST, ind[IN_LST], 0) },
 	{ FLDATA (ERR, ind[IN_READ], 0) },
 	{ FLDATA (S1, s1sel, 0) },
 	{ FLDATA (S2, s2sel, 0) },
 	{ DRDATA (POS, cdr_unit.pos, 31), PV_LEFT },
 	{ DRDATA (TIME, cdr_unit.wait, 24), PV_LEFT },
 	{ BRDATA (*BUF, rbuf, 8, 8, CDR_WIDTH), REG_HRO },
 	{ NULL }  };

 DEVICE cdr_dev = {
 	"CDR", &cdr_unit, cdr_reg, NULL,
 	1, 10, 31, 1, 8, 7,
 	NULL, NULL, &cd_reset,
 	&cdr_boot, &cdr_attach, NULL };

 /* CDP data structures

    cdp_dev	CDP device descriptor
    cdp_unit	CDP unit descriptor
    cdp_reg	CDP register list
 */

 UNIT cdp_unit = {
 	UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) };

 REG cdp_reg[] = {
 	{ FLDATA (ERR, ind[IN_PNCH], 0) },
 	{ FLDATA (S4, s4sel, 0) },
 	{ FLDATA (S8, s8sel, 0) },
 	{ DRDATA (POS, cdp_unit.pos, 31), PV_LEFT },
 	{ NULL }  };

 DEVICE cdp_dev = {
 	"CDP", &cdp_unit, cdp_reg, NULL,
 	1, 10, 31, 1, 8, 7,
 	NULL, NULL, &cd_reset,
 	NULL, NULL, NULL };

 /* Stacker data structures

    stack_dev	STACK device descriptor
    stack_unit	STACK unit descriptors
    stack_reg	STACK register list
 */

 UNIT stack_unit[] = {
 	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) },
 	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) },
 	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) },
 	{ UDATA (NULL, UNIT_DIS, 0) },			/* unused */
 	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) }  };

 REG stack_reg[] = {
 	{ DRDATA (POS0, stack_unit[0].pos, 31), PV_LEFT },
 	{ DRDATA (POS1, stack_unit[1].pos, 31), PV_LEFT },
 	{ DRDATA (POS28, stack_unit[2].pos, 31), PV_LEFT },
 	{ DRDATA (POS4, stack_unit[4].pos, 31), PV_LEFT },
 	{ NULL }  };

 DEVICE stack_dev = {
 	"STKR", stack_unit, stack_reg, NULL,
 	5, 10, 31, 1, 8, 7,
 	NULL, NULL, &cd_reset,
 	NULL, NULL, NULL };

 /* Card read routine

    Modifiers have been checked by the caller
    No modifiers are recognized (column binary is not implemented)
 */

 t_stat read_card (int32 ilnt, int32 mod)
 {
 int32 i;
 t_stat r;

 if (sim_is_active (&cdr_unit)) {			/* busy? */
 	sim_cancel (&cdr_unit);				/* cancel */
 	if (r = cdr_svc (&cdr_unit)) return r;  }	/* process */
 if ((cdr_unit.flags & UNIT_ATT) == 0) return SCPE_UNATT; /* attached? */
 ind[IN_READ] = ind[IN_LST] = s1sel = s2sel = 0;		/* default stacker */
 for (i = 0; i < CBUFSIZE; i++) rbuf[i] = 0;		/* clear buffer */
 fgets (rbuf, CBUFSIZE, cdr_unit.fileref);		/* read card */
 if (feof (cdr_unit.fileref)) return STOP_NOCD;		/* eof? */
 if (ferror (cdr_unit.fileref)) {			/* error? */
 	perror ("Card reader I/O error");
 	clearerr (cdr_unit.fileref);
 	if (iochk) return SCPE_IOERR;
 	ind[IN_READ] = 1;
 	return SCPE_OK;  }
 cdr_unit.pos = ftell (cdr_unit.fileref);		/* update position */
 if (ssa) {						/* if last cd on */
 	i = getc (cdr_unit.fileref);			/* see if more */
 	if (feof (cdr_unit.fileref)) ind[IN_LST] = 1;	/* eof? set flag */
 	fseek (cdr_unit.fileref, cdr_unit.pos, SEEK_SET);  }
 for (i = 0; i < CDR_WIDTH; i++) {			/* cvt to BCD */
 	rbuf[i] = ascii_to_bcd[rbuf[i]];
 	M[CDR_BUF + i] = (M[CDR_BUF + i] & WM) | rbuf[i];  }
 M[CDR_BUF - 1] = 060;					/* mem mark */
 sim_activate (&cdr_unit, cdr_unit.wait);		/* activate */
 return SCPE_OK;
 }

 /* Card reader service.  If a stacker select is active, copy to the
    selected stacker.  Otherwise, copy to the normal stacker.  If the
    unit is unattached, simply exit.
 */

 t_stat cdr_svc (UNIT *uptr)
 {
 int32 i;

 if (s1sel) uptr = &stack_unit[1];			/* stacker 1? */
 else if (s2sel) uptr = &stack_unit[2];			/* stacker 2? */
 else uptr = &stack_unit[0];				/* then default */
 if ((uptr -> flags & UNIT_ATT) == 0) return SCPE_OK;	/* attached? */
 for (i = 0; i < CDR_WIDTH; i++) rbuf[i] = bcd_to_ascii[rbuf[i]];
 for (i = CDR_WIDTH - 1; (i >= 0) && (rbuf[i] == ' '); i--) rbuf[i] = 0;
 rbuf[CDR_WIDTH] = 0;					/* null at end */
 fputs (rbuf, uptr -> fileref);				/* write card */
 fputc ('\n', uptr -> fileref);				/* plus new line */
 if (ferror (uptr -> fileref)) {				/* error? */
 	perror ("Card stacker I/O error");
 	clearerr (uptr -> fileref);
 	if (iochk) return SCPE_IOERR;  }
 uptr -> pos = ftell (uptr -> fileref);			/* update position */
 return SCPE_OK;
 }

 /* Card punch routine

    Modifiers have been checked by the caller
    No modifiers are recognized (column binary is not implemented)
 */

 t_stat punch_card (int32 ilnt, int32 mod)
 {
 int32 i;
 static char pbuf[CDP_WIDTH + 1];			/* + null */
 UNIT *uptr;

 if (s8sel) uptr = &stack_unit[2];			/* stack 8? */
 else if (s4sel) uptr = &stack_unit[4];			/* stack 4? */
 else uptr = &cdp_unit;					/* normal output */
 if ((uptr -> flags & UNIT_ATT) == 0) return SCPE_UNATT;	/* attached? */
 ind[IN_PNCH] = s4sel = s8sel = 0;			/* clear flags */

 M[CDP_BUF - 1] = 012;					/* set prev loc */
 for (i = 0; i < CDP_WIDTH; i++) pbuf[i] = bcd_to_ascii[M[CDP_BUF + i] & CHAR];
 for (i = CDP_WIDTH - 1; (i >= 0) && (pbuf[i] == ' '); i--) pbuf[i] = 0;
 pbuf[CDP_WIDTH] = 0;					/* trailing null */
 fputs (pbuf, uptr -> fileref);				/* output card */
 fputc ('\n', uptr -> fileref);				/* plus new line */
 if (ferror (uptr -> fileref)) {				/* error? */
 	perror ("Card punch I/O error");
 	clearerr (uptr -> fileref);
 	if (iochk) return SCPE_IOERR;
 	ind[IN_PNCH] = 1;  }
 uptr -> pos = ftell (uptr -> fileref);			/* update position */
 return SCPE_OK;
 }

 /* Select stack routine

    Modifiers have been checked by the caller
    Modifiers are 1, 2, 4, 8 for the respective stack
 */

 t_stat select_stack (int32 ilnt, int32 mod)
 {
 if (mod == 1) s1sel = 1;
 else if (mod == 2) s2sel = 1;
 else if (mod == 4) s4sel = 1;
 else if (mod == 8) s8sel = 1;
 return SCPE_OK;
 }

 /* Card reader/punch reset */

 t_stat cd_reset (DEVICE *dptr)
 {
 ind[IN_LST] = ind[IN_READ] = ind[IN_PNCH] = 0;		/* clear indicators */
 s1sel = s2sel = s4sel = s8sel = 0;			/* clear stacker sel */
 sim_cancel (&cdr_unit);					/* clear reader event */
 return SCPE_OK;
 }

 /* Card reader attach */

 t_stat cdr_attach (UNIT *uptr, char *cptr)
 {
 ind[IN_LST] = ind[IN_READ] = 0;				/* clear last card */
 return attach_unit (uptr, cptr);
 }

 /* Bootstrap routine */

 #define BOOT_START 100
 #define BOOT_LEN (sizeof (boot_rom) / sizeof (unsigned char))

 static const unsigned char boot_rom[] = {
 	OP_R + WM,					/* R */
 	OP_SWM + WM, BCD_ZERO, BCD_ZERO, BCD_ONE,	/* SWM 001 */
 	OP_CS + WM, BCD_ZERO, BCD_ZERO, BCD_ONE,	/* CS 001 111 */
 		BCD_ONE, BCD_ONE, BCD_ONE  };

 t_stat cdr_boot (int32 unitno)
 {
 int32 i;
 extern int32 saved_IS;

 for (i = 0; i < CDR_WIDTH; i++) M[CDR_BUF + i] = 0;	/* clear buffer */
 for (i = 0; i < BOOT_LEN; i++) M[BOOT_START + i] = boot_rom[i];
 saved_IS = BOOT_START;
 return SCPE_OK;
 }
	/* i1401_cd.c: IBM 1402 card reader/punch

	Copyright (c) 1993-2000, 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
	ROBERT M SUPNIK 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 Robert M Supnik shall not
	be used in advertising or otherwise to promote the sale, use or other dealings
	in this Software without prior written authorization from Robert M Supnik.

	cdr card reader
	cdp card punch
	stack stackers (5 units)
	0 normal
	1 1
	2 2/8
	3 unused
	4 4

	Cards are represented as ASCII text streams terminated by newlines.
	This allows cards to be created and edited as normal files.
	*/

	#include "i1401_defs.h"
	#include <ctype.h>

	extern unsigned char M[];
	extern int32 ind[64], ssa, iochk;
	extern char bcd_to_ascii[64];
	extern char ascii_to_bcd[128];
	int32 s1sel, s2sel, s4sel, s8sel;
	char rbuf[CBUFSIZE]; /* > CDR_WIDTH */
	t_stat cdr_svc (UNIT *uptr);
	t_stat cdr_boot (int32 unitno);
	t_stat cdr_attach (UNIT uptr, char cptr);
	t_stat cd_reset (DEVICE *dptr);
	extern t_stat sim_activate (UNIT *uptr, int32 delay);
	extern t_stat sim_cancel (UNIT *uptr);
	extern int32 sim_is_active (UNIT *uptr);

	/* Card reader data structures

	cdr_dev CDR descriptor
	cdr_unit CDR unit descriptor
	cdr_reg CDR register list
	*/

	UNIT cdr_unit = {
	UDATA (&cdr_svc, UNIT_SEQ+UNIT_ATTABLE, 0), 100 };

	REG cdr_reg[] = {
	{ FLDATA (LAST, ind[IN_LST], 0) },
	{ FLDATA (ERR, ind[IN_READ], 0) },
	{ FLDATA (S1, s1sel, 0) },
	{ FLDATA (S2, s2sel, 0) },
	{ DRDATA (POS, cdr_unit.pos, 31), PV_LEFT },
	{ DRDATA (TIME, cdr_unit.wait, 24), PV_LEFT },
	{ BRDATA (*BUF, rbuf, 8, 8, CDR_WIDTH), REG_HRO },
	{ NULL } };

	DEVICE cdr_dev = {
	"CDR", &cdr_unit, cdr_reg, NULL,
	1, 10, 31, 1, 8, 7,
	NULL, NULL, &cd_reset,
	&cdr_boot, &cdr_attach, NULL };

	/* CDP data structures

	cdp_dev CDP device descriptor
	cdp_unit CDP unit descriptor
	cdp_reg CDP register list
	*/

	UNIT cdp_unit = {
	UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) };

	REG cdp_reg[] = {
	{ FLDATA (ERR, ind[IN_PNCH], 0) },
	{ FLDATA (S4, s4sel, 0) },
	{ FLDATA (S8, s8sel, 0) },
	{ DRDATA (POS, cdp_unit.pos, 31), PV_LEFT },
	{ NULL } };

	DEVICE cdp_dev = {
	"CDP", &cdp_unit, cdp_reg, NULL,
	1, 10, 31, 1, 8, 7,
	NULL, NULL, &cd_reset,
	NULL, NULL, NULL };

	/* Stacker data structures

	stack_dev STACK device descriptor
	stack_unit STACK unit descriptors
	stack_reg STACK register list
	*/

	UNIT stack_unit[] = {
	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) },
	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) },
	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) },
	{ UDATA (NULL, UNIT_DIS, 0) }, /* unused */
	{ UDATA (NULL, UNIT_SEQ+UNIT_ATTABLE, 0) } };

	REG stack_reg[] = {
	{ DRDATA (POS0, stack_unit[0].pos, 31), PV_LEFT },
	{ DRDATA (POS1, stack_unit[1].pos, 31), PV_LEFT },
	{ DRDATA (POS28, stack_unit[2].pos, 31), PV_LEFT },
	{ DRDATA (POS4, stack_unit[4].pos, 31), PV_LEFT },
	{ NULL } };

	DEVICE stack_dev = {
	"STKR", stack_unit, stack_reg, NULL,
	5, 10, 31, 1, 8, 7,
	NULL, NULL, &cd_reset,
	NULL, NULL, NULL };

	/* Card read routine

	Modifiers have been checked by the caller
	No modifiers are recognized (column binary is not implemented)
	*/

	t_stat read_card (int32 ilnt, int32 mod)
	{
	int32 i;
	t_stat r;

	if (sim_is_active (&cdr_unit)) { /* busy? */
	sim_cancel (&cdr_unit); /* cancel */
	if (r = cdr_svc (&cdr_unit)) return r; } /* process */
	if ((cdr_unit.flags & UNIT_ATT) == 0) return SCPE_UNATT; /* attached? */
	ind[IN_READ] = ind[IN_LST] = s1sel = s2sel = 0; /* default stacker */
	for (i = 0; i < CBUFSIZE; i++) rbuf[i] = 0; /* clear buffer */
	fgets (rbuf, CBUFSIZE, cdr_unit.fileref); /* read card */
	if (feof (cdr_unit.fileref)) return STOP_NOCD; /* eof? */
	if (ferror (cdr_unit.fileref)) { /* error? */
	perror ("Card reader I/O error");
	clearerr (cdr_unit.fileref);
	if (iochk) return SCPE_IOERR;
	ind[IN_READ] = 1;
	return SCPE_OK; }
	cdr_unit.pos = ftell (cdr_unit.fileref); /* update position */
	if (ssa) { /* if last cd on */
	i = getc (cdr_unit.fileref); /* see if more */
	if (feof (cdr_unit.fileref)) ind[IN_LST] = 1; /* eof? set flag */
	fseek (cdr_unit.fileref, cdr_unit.pos, SEEK_SET); }
	for (i = 0; i < CDR_WIDTH; i++) { /* cvt to BCD */
	rbuf[i] = ascii_to_bcd[rbuf[i]];
	M[CDR_BUF + i] = (M[CDR_BUF + i] & WM) \| rbuf[i]; }
	M[CDR_BUF - 1] = 060; /* mem mark */
	sim_activate (&cdr_unit, cdr_unit.wait); /* activate */
	return SCPE_OK;
	}

	/* Card reader service. If a stacker select is active, copy to the
	selected stacker. Otherwise, copy to the normal stacker. If the
	unit is unattached, simply exit.
	*/

	t_stat cdr_svc (UNIT *uptr)
	{
	int32 i;

	if (s1sel) uptr = &stack_unit[1]; /* stacker 1? */
	else if (s2sel) uptr = &stack_unit[2]; /* stacker 2? */
	else uptr = &stack_unit[0]; /* then default */
	if ((uptr -> flags & UNIT_ATT) == 0) return SCPE_OK; /* attached? */
	for (i = 0; i < CDR_WIDTH; i++) rbuf[i] = bcd_to_ascii[rbuf[i]];
	for (i = CDR_WIDTH - 1; (i >= 0) && (rbuf[i] == ' '); i--) rbuf[i] = 0;
	rbuf[CDR_WIDTH] = 0; /* null at end */
	fputs (rbuf, uptr -> fileref); /* write card */
	fputc ('\n', uptr -> fileref); /* plus new line */
	if (ferror (uptr -> fileref)) { /* error? */
	perror ("Card stacker I/O error");
	clearerr (uptr -> fileref);
	if (iochk) return SCPE_IOERR; }
	uptr -> pos = ftell (uptr -> fileref); /* update position */
	return SCPE_OK;
	}

	/* Card punch routine

	Modifiers have been checked by the caller
	No modifiers are recognized (column binary is not implemented)
	*/

	t_stat punch_card (int32 ilnt, int32 mod)
	{
	int32 i;
	static char pbuf[CDP_WIDTH + 1]; /* + null */
	UNIT *uptr;

	if (s8sel) uptr = &stack_unit[2]; /* stack 8? */
	else if (s4sel) uptr = &stack_unit[4]; /* stack 4? */
	else uptr = &cdp_unit; /* normal output */
	if ((uptr -> flags & UNIT_ATT) == 0) return SCPE_UNATT; /* attached? */
	ind[IN_PNCH] = s4sel = s8sel = 0; /* clear flags */

	M[CDP_BUF - 1] = 012; /* set prev loc */
	for (i = 0; i < CDP_WIDTH; i++) pbuf[i] = bcd_to_ascii[M[CDP_BUF + i] & CHAR];
	for (i = CDP_WIDTH - 1; (i >= 0) && (pbuf[i] == ' '); i--) pbuf[i] = 0;
	pbuf[CDP_WIDTH] = 0; /* trailing null */
	fputs (pbuf, uptr -> fileref); /* output card */
	fputc ('\n', uptr -> fileref); /* plus new line */
	if (ferror (uptr -> fileref)) { /* error? */
	perror ("Card punch I/O error");
	clearerr (uptr -> fileref);
	if (iochk) return SCPE_IOERR;
	ind[IN_PNCH] = 1; }
	uptr -> pos = ftell (uptr -> fileref); /* update position */
	return SCPE_OK;
	}

	/* Select stack routine

	Modifiers have been checked by the caller
	Modifiers are 1, 2, 4, 8 for the respective stack
	*/

	t_stat select_stack (int32 ilnt, int32 mod)
	{
	if (mod == 1) s1sel = 1;
	else if (mod == 2) s2sel = 1;
	else if (mod == 4) s4sel = 1;
	else if (mod == 8) s8sel = 1;
	return SCPE_OK;
	}

	/* Card reader/punch reset */

	t_stat cd_reset (DEVICE *dptr)
	{
	ind[IN_LST] = ind[IN_READ] = ind[IN_PNCH] = 0; /* clear indicators */
	s1sel = s2sel = s4sel = s8sel = 0; /* clear stacker sel */
	sim_cancel (&cdr_unit); /* clear reader event */
	return SCPE_OK;
	}

	/* Card reader attach */

	t_stat cdr_attach (UNIT uptr, char cptr)
	{
	ind[IN_LST] = ind[IN_READ] = 0; /* clear last card */
	return attach_unit (uptr, cptr);
	}

	/* Bootstrap routine */

	#define BOOT_START 100
	#define BOOT_LEN (sizeof (boot_rom) / sizeof (unsigned char))

	static const unsigned char boot_rom[] = {
	OP_R + WM, /* R */
	OP_SWM + WM, BCD_ZERO, BCD_ZERO, BCD_ONE, /* SWM 001 */
	OP_CS + WM, BCD_ZERO, BCD_ZERO, BCD_ONE, /* CS 001 111 */
	BCD_ONE, BCD_ONE, BCD_ONE };

	t_stat cdr_boot (int32 unitno)
	{
	int32 i;
	extern int32 saved_IS;

	for (i = 0; i < CDR_WIDTH; i++) M[CDR_BUF + i] = 0; /* clear buffer */
	for (i = 0; i < BOOT_LEN; i++) M[BOOT_START + i] = boot_rom[i];
	saved_IS = BOOT_START;
	return SCPE_OK;
	}