# Vic 20 Memory Expansion

Available on Commodore Vic 20 computers. On the left side.

      1               TOP              22
    +-------------------//----------------+
    | =================//================ |
    +-----------------//------------------+
      A              BOTTOM             Z

(at the Computer)

UNKNOWN CONNECTOR at the Computer.

Pin | Name | Description
--- | --- | ---
A | GND | Ground
B | CA0 | Address 0
C | CA1 | Address 1
D | CA2 | Address 2
E | CA3 | Address 3
F | CA4 | Address 4
H | CA5 | Address 5
J | CA6 | Address 6
K | CA7 | Address 7
L | CA8 | Address 8
M | CA9 | Address 9
N | CA10 | Address 10
P | CA11 | Address 11
R | CA12 | Address 12
S | CA13 | Address 13
T | I/O 2 | Decoded I/O block 2, starting at $9130
U | I/O 3 | Decoded I/O block 3, starting at $9140
V | S02 | Phase 2 System Clock
W | /NMI | Non maskable Interrupt
X | /RESET | 6502 Reset
Y | n/c | Not connected
Z | GND | Ground
1 | GND | Ground
2 | CD0 | Data 0
3 | CD1 | Data 1
4 | CD2 | Data 2
5 | CD3 | Data 3
6 | CD4 | Data 4
7 | CD5 | Data 5
8 | CD6 | Data 6
9 | CD7 | Data 7
10 | /BLK 1 | BLK 1 (Memory location $2000 - $3fff)
11 | /BLK 2 | BLK 2 (Memory location $4000 - $5fff)
12 | /BLK 3 | BLK 3 (Memory location $6000 - $7fff)
13 | /BLK 5 | BLK 5 (Memory location $a000 - $bfff)
14 | RAM 1 | RAM 1 (Memory location $0400 - $07ff)
15 | RAM 2 | RAM 2 (Memory location $0800 - $0bff)
16 | RAM 3 | RAM 3 (Memory location $0c00 - $0fff)
17 | V R/W | Read/Write from Vic chip (1=R, 0=W)
18 | C R/W | Read/Write from CPU (1=R, 0=W)
19 | /IRQ | 6502 Interrupt Request
20 | n/c | Not connected
21 | +5V | +5 VDC
22 | GND | Ground

Contributor: | Joakim Ögren

Source: | Inside your Vic 20 by Ward Shrake
| "The Vic Revealed" by Nick Hampshire, 1982, Hayden Book Co, Inc.
| "Vic20 Programmer's Reference Guide", 1992, Commodore Business, Machines, Inc. and Howard W. Sams & Company, Inc.

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