# 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 1996-2001.
May be copied and redistributed, partially or in whole, as appropriate.
Document last modified: 2001-06-08