From: Adam.Bergstrom@um.erisoft.se (Adam Bergstrom)
Newsgroups: comp.sys.cbm
Subject: VIC-20 extra memory, UPGRADE
Date: 27 Oct 1995 06:30:38 GMT


Well, I thought about the bus-collision, and found a way of dealing
with it (it's actually simpler now). This is the new version, that 
won't fry the bus when writing to write-protected memory. 
It has also got 1 less component (a resistor) :) .


VIC-20 32k memory expansion (ver. 951026)
=========================================

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!


Features
--------

* 32k RAM in four 8k blocks located in memory at:
  
  $2000 (BLK1)
  $4000 (BLK2)
  $6000 (BLK3)
  $A000 (BLK5)

  This gives you an additional 24k BASIC memory (27,5k total!), and 8k at the
  cartridge area.

* Ability to load and run cartridge-images from disk or tape. 

* Write enable/disable switch, lets you run copyprotected cartridgeimages.

* Switch to enable/disable the whole extra-memory, to let you use an external 
  cartridge, or use the VIC-20 unexpanded.

* Reset switch.



Parts used
----------

1 * HY62256, 32kbyte static RAM, 100ns (any 32k SRAM faster than 500ns should 
    be O.K.)
1 * 74LS147, 10-4 line priority encoder
2 * on/off switches
1 * reset switch
Some wires and a vero-board to solder all parts on.


How to connect it all
---------------------

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)


Memory expansion port, seen from the back of the VIC-20
-------------------------------------------------------


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


Static memory HY62256 (SRAM), pinconfiguration
----------------------------------------------

    +---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
    +-------+


74LS147, pinconfiguration
-------------------------

    +---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
    +-------+


On/off switch
-------------

       /
      /
   --+--
   |   |
   |   |
   -----
   | | |
   1 2 3


How to contact me
-----------------

Snail mail:
  Adam Bergstrom
  Storgatan 92,2
  903 33 Umea
  SWEDEN

Telephone:
  +46-90-178490

Internet email:
  adam.bergstrom@um.erisoft.se
 
+-----------------+-----------------------------------------------+
|Snail-mail work: |E-mail work: adam.bergstrom@um.erisoft.se      |
| Adam Bergstrom  +--------------------------+--------------------+
| Erisoft AB      |Memo work: eri.epl.eplabm |Snail-mail home:    |
| Pendelgatan 2   +--------------------------+ Adam Bergstrom     |
| Box 4205        |Telephone:                | Storgatan 92       |
| S-904 06 Umea   | Work: +46 (0)90 153136   | S-903 33 Umea      |
| Sweden          | Home: +46 (0)90 178490   | Sweden             |
+-----------------+--------------------------+--------------------+
| Opinions expressed are my own, not my employer's.               |
+-----------------------------------------------------------------+
                                                                         





