GAL logic equations file by Lee Davison.
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This file includes the equations for the ISA slot logic as well as the ROM/RAM expansion logic. Only those lines that are needed for the ROM/RAM expansion have been rendered in bold.

By changing the lines that define the ROM and RAM any one of a number possible combinations of ROM and RAM can be accommodated. 


Name     vic_ISA ;
PartNo   00 ;
Date     01/10/03 ;
Revision 01 ;
Designer Lee ;
Company  ;
Assembly None ;
Location  ;
Device   g16v8as ;

/* This is the glue for the vic 20 ISA card & RAM/ROM expansion	*/	

/* Logic minimisations			None			*/
/* Optimizations			None			*/
/* Download				JEDEC/POF/PRG		*/
/* Doc File Options			fuse plot, equations	*/
/* Output				None			*/

/* INPUT PINS 							*/

PIN	1 = dlp2	;		/* delayed phase 2	*/
PIN	2 = VRW		;		/* VIC read write	*/
PIN	3 = !BLK1	;		/* block select		*/
PIN	4 = !BLK2	;		/* block select		*/
PIN	5 = !BLK3	;		/* block select		*/
PIN	6 = !BLK5	;		/* block select		*/
PIN	7 = CRW		;		/* CPU read write	*/
PIN	8 = p2		;		/* phase 2		*/
PIN	9 = !IO3	;		/* I/O access		*/
PIN	11 = !RES	;		/* reset		*/

/* OUTPUT PINS							*/

PIN  19 = ROM		;		/* 8/16/24/32K ROM	*/
PIN  18 = RAM		;		/* 8/16/24/32K RAM	*/
PIN  17 = ROM_A14	;		/* ROM address line	*/
PIN  16 = A13		;		/* ROM/RAM address line	*/
PIN  15 = RAM_A14	;		/* RAM address line	*/ 
PIN  14 = ISA_RES	;		/* ISA card reset line	*/
PIN  13 = ISA_IOW	;		/* ISA card I/O write	*/
PIN  12 = ISA_IOR	;		/* ISA card I/O read	*/

/* Output terms							*/

/* comment out the RAM/ROM configuration lines you don't want	*/

/* 24K expansion RAM with 8K ROM in the autostart block		*/
/* $2000 = RAM	$4000 = RAM	$6000 = RAM	$A000 = ROM	*/
/*!ROM	= BLK5 ;			/* 8/16/24/32K ROM	*/
/*!RAM	= BLK1 # BLK2 # BLK3 ;		/* 8/16/24/32K RAM	*/

/* 16K expansion RAM with 16K autostart game ROM		*/
/* $2000 = RAM	$4000 = RAM	$6000 = ROM	$A000 = ROM	*/
!ROM	= BLK3 # BLK5 ;			/* 8/16/24/32K ROM	*/
!RAM	= BLK1 # BLK2 ;			/* 8/16/24/32K RAM	*/

!ROM_A14 = BLK1 # BLK5 ;		/* ROM address line	*/
!A13	= BLK2 # BLK5 ;			/* ROM/RAM address line	*/
!RAM_A14 = BLK1 # BLK5 ;		/* RAM address line	*/
ISA_RES	= RES ;				/* ISA card reset line	*/
!ISA_IOW = !CRW & IO3 & p2 & dlp2 ;	/* ISA card I/O write	*/
!ISA_IOR = CRW & IO3 & p2 & dlp2 ;	/* ISA card I/O read	*/

Last page update: 26th February, 2004. e-mail me