Apple Macintosh Portable ROM Expansion

50 PIN UNKNOWN CONNECTOR

Pin	Name	Description
1	+5V	+5 VDC
2	A1	Address bit 1
3	A2	Address bit 2
4	A3	Address bit 3
5	A4	Address bit 4
6	A5	Address bit 5
7	A6	Address bit 6
8	A7	Address bit 7
9	A8	Address bit 8
10	A9	Address bit 9
11	A10	Address bit 10
12	A11	Address bit 11
13	A12	Address bit 12
14	A13	Address bit 13
15	A14	Address bit 14
16	A15	Address bit 15
17	A16	Address bit 16
18	A17	Address bit 17
19	A18	Address bit 18
20	A19	Address bit 19
21	A20	Address bit 20
22	A21	Address bit 21
23	A22	Address bit 22
24	A23	Address bit 23
25	GND	Ground
26	GND	Ground
27	/DTACK	Data Transfer Acknowledge
28	/AS	Address Strobe
29	/ROM_CS	ROM Chip Select
30	16M	16 MHz Clock
31	/EXT_DTACK	External Data Transfer Acknowledge
32	/DELAY_CS
33	D0	Data bit 0
34	D1	Data bit 1
35	D2	Data bit 2
36	D3	Data bit 3
37	D4	Data bit 4
38	D5	Data bit 5
39	D6	Data bit 6
40	D7	Data bit 7
41	D8	Data bit 8
42	D9	Data bit 9
43	D10	Data bit 10
44	D11	Data bit 11
45	D12	Data bit 12
46	D13	Data bit 13
47	D14	Data bit 14
48	D15	Data bit 15
49	+5V	+5 VDC
50	+5V	+5 VDC

D0-D15

Unbuffered data bus, bits 0 through 15

Unbuffered 68HC000 address bus, bits 1 through 23

16 MHz system clock

External data transfer acknowledge that disables main system /DTACK.

68HC000 Address strobe

Data transfer acknowledge, /DTACK input to 68HC000.

This signal is generated by the addressing PAL and is used to put the ROM board into the idle mode by inserting multiple wait states.

Permanent ROM chip select signal. Selects in range $90 0000 through $9F FFFF.

Contributor:

Joakim Ögren

Source:

Technote HW13: Macintosh Portable ROM Expansion at Apple Technical Notes