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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

A1-A23

Unbuffered 68HC000 address bus, bits 1 through 23

16M

16 MHz system clock

/EXT.DTACK

External data transfer acknowledge that disables main system /DTACK.

/AS

68HC000 Address strobe

/DTACK

Data transfer acknowledge, /DTACK input to 68HC000.

/DELAY_CS

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.

/ROM_CS

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

Copyright © The Hardware Book Team 1996-2004.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2002-01-10