# C128 Expansion Bus

Available at the Commodore 128.

(at the computer)

44 PIN FEMALE EDGE at the computer.

Pin | Name | Description
--- | --- | ---
1 | GND | System Ground
2 | +5V | System Vcc
3 | +5V | System Vcc
4 | /IRQ | Interrupt request
5 | R/W | System Read/Write Signal
6 | DClock | 8.18MHz Video Dot Clock
7 | I/O1 | I/O Chip select $de00-deff
8 | /GAME | Sensed for memory map configuration
9 | /EXROM | Sensed for memory map configuration
10 | I/O2 | I/O Chip select $df00-dfff
11 | /ROML | External ROM select $8000-Bfff
12 | BA | Bus available output
13 | /DMA | Direct memory access input
14 | D7 | Data bit 7
15 | D6 | Data bit 6
16 | D5 | Data bit 5
17 | D4 | Data bit 4
18 | D3 | Data bit 3
19 | D2 | Data bit 2
20 | D1 | Data bit 1
21 | D0 | Data bit 0
22 | GND | System Ground
A | GND | System Ground
B | /ROMH | External ROM Select $c000-ffff
C | /RESET | System Reset Signal
D | /NMI | Non-Maskable Interrupt
E | 1MHz | System 1MHz clock
F | TA15 | Translated address bit 15
H | TA14 | Translated address bit 14
J | TA13 | Translated address bit 13
K | TA12 | Translated address bit 12
L | TA11 | Translated address bit 11
M | TA10 | Translated address bit 10
N | TA9 | Translated address bit 9
P | TA8 | Translated address bit 8
R | SA7 | Shared address bit 7
S | SA6 | Shared address bit 6
T | SA5 | Shared address bit 5
U | SA4 | Shared address bit 4
V | SA3 | Shared address bit 3
W | SA2 | Shared address bit 2
X | SA1 | Shared address bit 1
Y | SA0 | Shared address bit 0
Z | GND | System Ground

Contributor: Rob Gill

Source:
Commodore 128 Programmers reference guide

Copyright © The Hardware Book Team 1996-2001.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2001-06-07