/* Imported from Wayback Machine

 Original URL : https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:grc:conn_def
 Snapshot date: 2024-01-15
 Generator    : wayback-archiver

*/

Generic Retro Computer Bus Definition

The expansion connector for GRC modules is a 2×25, 2.54mm spacing female header on the backplane and a corresponding right-angle male connector on each module. The following is the pin assignment of the GRC expansion connector.

Pin Number	Signal Name	Description
1	GND	Ground
2	VCC	+5V
3	nCS5	Chip select #5, active low
4	D7	Data bus 7, bidirection
5	nCS4	Chip select #4, active low
6	D6	Data bus 6, bidirection
7	nCS3	Chip select #3, active low
8	D5	Data bus 5, bidirection
9	nCS2	Chip select #2, active low
10	D4	Data bus 4, bidirection
11	nCS1	Chip select #1, active low
12	D3	Data bus 3, bidirection
13	nWRCF	Compact flash write strobe, active low
14	D2	Data bus 2, bidirection
15	nRDCF	Compact flash read strobe, active low
16	D1	Data bus 1, bidirection
17	nCSCF	Compact flash chip select, active low
18	D0	Data bus 0, bidirection
19	nCSRAM	RAM chip select
20	CPU Ctrl4	CPU-specific control line
21	nNMI	Non-maskable interrupt
22	CPU Ctrl3	CPU-specific control line
23	nWAIT	CPU wait, active low
24	nWR	Write, active low
25	Bank3	Memory bank select, MSB
26	CPU Ctrl2	CPU-specific control line
27	Bank2	Memory bank select
28	CPU Ctrl1	CPU-specific control line
29	Bank1	Memory bank select
30	nIRQ	Interrupt
31	Bank0	Memory bank select, LSB
32	nRESET	System reset, active low
33	A15	Address line, MSB
34	CLK	System clock
35	A14	Address line
36	A0	Address line, LSB
37	A13	Address line
38	A1	Address line
39	A12	Address line
40	A2	Address line
41	A11	Address line
42	A3	Address line
43	A10	Address line
44	A4	Address line
45	A9	Address line
46	A5	Address line
47	A8	Address line
48	A6	Address line
49	GND	Ground
50	A7	Address line