by Adam Bergström (adam.bergstrom@um.erisoft.se)
This is one of my contributions to the Commodore 8-bit community. I made this document to show you how to expand the memory of your VIC-20. I designed and built the memory expansion in October 1995.
I have built the expansion on a vero-board inside my VIC-20, so the cartridge port is free. All that is seen outside are three switches (reset, write enable/disable, memoryexpansion on/off).
I also plan to make an external memory-cartridge (so I can make some for my friends without opening their precious babies) as soon as I get all the stuff to make PCB:s at work.
This new version has removed the trouble with bus-collision.
I hope that this document is accurate and that you can get it to work. My hardware DOES work, and has been tested on quite a few programs, both expanded, unexpanded, and cartridgeimages (both 8k and 16k).
I will take no responsibility for any damages that may occur when you are trying to use this information. This information is free, and any damages are done by you, not me.
Let the old 8-bit computers LIVE ON!
SRAM_X is pin nr X on SRAM. 74_X is pin nr X on 74LS147. VIC_X is pin nr X on VIC expansion port. SWITCHX_Y is switch nr X, pin nr Y. SWITCH1 is write enable/disable. SWITCH2 is expansion enable/disable. SWITCH3 is reset. SRAM_1(A14) - 74_9(A) SRAM_2(A12) - VIC_R(CA12) SRAM_3(A7) - VIC_K(CA7) SRAM_4(A6) - VIC_J(CA6) SRAM_5(A5) - VIC_H(CA5) SRAM_6(A4) - VIC_F(CA4) SRAM_7(A3) - VIC_E(CA3) SRAM_8(A2) - VIC_D(CA2) SRAM_9(A1) - VIC_C(CA1) SRAM_10(A0) - VIC_B(CA0) SRAM_11(D0) - VIC_2(CD0) SRAM_12(D1) - VIC_3(CD1) SRAM_13(D2) - VIC_4(CD2) SRAM_14(GND) - VIC_GND SRAM_15(D3) - VIC_5(CD3) SRAM_16(D4) - VIC_6(CD4) SRAM_17(D5) - VIC_7(CD5) SRAM_18(D6) - VIC_8(CD6) SRAM_19(D7) - VIC_9(CD7) SRAM_20(!CE) - 74_6(C) SRAM_21(A10) - VIC_N(CA10) SRAM_22(!OE) - 74_6(C) SRAM_23(A11) - VIC_P(CA11) SRAM_24(A9) - VIC_M(CA9) SRAM_25(A8) - VIC_L(CA8) SRAM_26(A13) - 74_7(B) SRAM_27(R/W) - VIC_18(CR/W) SRAM_28(VDD) - VIC_21(+5V) 74_1(4) - VIC_10(!BLK1) 74_2(5) - VIC_11(!BLK2) 74_3(6) - VIC_12(!BLK3) 74_4(7) - VIC_13(!BLK5) 74_5(8) - SWITCH1_2 74_6(C) - SRAM_20(!CE) + SRAM_22(!OE) 74_7(B) - SRAM_26(A13) 74_8(GND) - VIC_GND 74_9(A) - SRAM_1(A14) 74_10(9) - SWITCH2_2 74_11(1) - VIC_GND 74_12(2) - VIC_GND 74_13(3) - VIC_GND 74_14(D) - NC 74_15(NC) - NC 74_16(VCC) - VIC_21(+5V) SWITCH1_1 - VIC_18(CR/W) SWITCH1_2 - 74_5(8) SWITCH1_3 - VIC_21(+5V) SWITCH2_1 - VIC_GND SWITCH2_2 - 74_10(9) SWITCH2_3 - VIC_21(+5V) SWITCH3_1 - VIC_GND SWITCH3_2 - VIC_X(RESET)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A B C D E F H J K L M N P R S T U V W X Y Z 1 - GND A - GND 2 - CD0 B - CA0 3 - CD1 C - CA1 4 - CD2 D - CA2 5 - CD3 E - CA3 6 - CD4 F - CA4 7 - CD5 H - CA5 8 - CD6 J - CA6 9 - CD7 K - CA7 10 - !BLK1 L - CA8 11 - !BLK2 M - CA9 12 - !BLK3 N - CA10 13 - !BLK5 P - CA11 14 - !RAM1 R - CA12 15 - !RAM2 S - CA13 16 - !RAM3 T - I/O2 17 - VR/W U - I/O3 18 - CR/W V - SO2 19 - !IRQ W - !NMI 20 - NC X - !RESET 21 - +5V Y - NC 22 - GND Z - GND
+---U---+
A14-|1 28|-VDD
A12-|2 27|-R/W
A7-|3 26|-A13
A6-|4 25|-A8
A5-|5 24|-A9
A4-|6 23|-A11
A3-|7 22|-!OE
A2-|8 21|-A10
A1-|9 20|-!CE
A0-|10 19|-D7
D0-|11 18|-D6
D1-|12 17|-D5
D2-|13 16|-D4
GND-|14 15|-D3
+-------+
+---U---+
4-|1 16|-VCC
5-|2 15|-NC
6-|3 14|-D
7-|4 13|-3
8-|5 12|-2
C-|6 11|-1
B-|7 10|-9
GND-|8 9|-A
+-------+
/
/
--+--
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