# Device list: VIC-20

g.baltissen_at_hccnet.nl
Date: 2000-12-09 11:11:14

```Hallo allemaal,

Yesterday I opened two different VIC-20's to check what was inside. Then I
checked the SCH to see in what addressrange the RAM etc. must show up (I
wanted to include mirroring as well). I run into some problems so I need
the help of some VIC-20 experts, please.

VIC-I:
The book says 9000-900F but I have no idea how this is realised. A15..13
are combined into VA13. VA0..12 are mirrors of CA0..12. My conclusion is

VIA's:
The book says 911x and 912x. The first selection is done by I/O0 =
9000-93FF. Second selection is made by CA5 or CA4.this means:
UAB1 = 1001 00xx xxx1 xxxx
UAB3 = 1001 00xx xx1x xxxx
911x and 912x are just a part of the found ranges but then my question is:
why not 901x and 902x?

Colour RAM:
My book, "VIC  revealed" by Nick Hampshire, says colour RAM is at 9600
unless there is more than 3K of expansion memory. In that case you'll find
it at 9800 (page 112).
My SCH says:
1001 00xx xxxx xxxx = 9000-93FF = I/O0
1001 01xx xxxx xxxx = 9400-97FF = COLOR
1001 10xx xxxx xxxx = 9800-9BFF = I/O2
1001 11xx xxxx xxxx = 9C00-9FFF = I/O3
The VIC only needs 506 bytes which would fit in the ranges 9400-95FF or
9600-97FF. So my first guess is a typing error of the author or printer.
Another question: what is the idea behind changing the range in case of
more memory? (I cannot see any profit in it)

Here is the first result for those VIC-20's to give you an idea how the
list could look like:

VIC-20

ASSY NO.324003FAB NO. 324002-02 REV.D

UAB1     9120-912F  VIA                          6522
UAB3     9110-911F  VIA                          6522
UB4                 6 * OC invertor              7406
UB7      9000-900F  VIC-I                        6561
UB6                                              NE555
UB9                 4 * 2-NOR                    M53202
UB10                D-Flipflop                   74S74
UC2                 6 * invertor                 74LS04
UC3                 4 * 2-NOR                    74LS02
UC4                 3 t0 8 multiplexer           74LS138
UC5                 3 t0 8 multiplexer           74LS138
UC6                 3 t0 8 multiplexer           74LS138
UD1                 4 * analogue switch          4066
UD2..6              1K*4 RAM                     MM2114-3
UD7      8000-8FFF  CHARACTER ROM                901460-03
UD8                 8-bit buffer                 74LS245
UD9                 1 * 13-NAND                  74LS133
UE1..6              1K*4 RAM                     MM2114-3
UE8                 8-bit buffer                 74LS245
UE10                CPU                          6502
UE11     C000-EFFF  BASIC ROM                    901486-01
UE12     E000-FFFF  KERNAL ROM                   901486-07
UF8                 8-bit buffer                 74LS245
U13                 4 * 2-AND                    74LS08
U14                 2K*8 RAM                     HM6116-4
U15                 2K*8 RAM                     HM6116-4

ASSY NO.250403       FAB NO. 251040-01 REV.D

UAB1     9120-912F  VIA                          6522
UAB3     9110-911F  VIA                          6522
UB4                 6 * OC invertor              7406
UB6                                              UA555
UB7      9000-900F  VIC-I                        6561
UB9                 4 * 2-NOR                    7402
UC2                 6 * invertor                 74LS04
UC3                 4 * 2-NOR                    74LS02
UC4                 3 t0 8 multiplexer           74S138
UC5                 3 t0 8 multiplexer           74S138
UC6                 3 t0 8 multiplexer           74S138
UD1                 4 * analogue switch          4066
UD2                 1K*4 RAM                     MM2114-3
UD7      8000-8FFF  CHARACTER ROM                901460-03
UD8                 8-bit buffer                 65245
UD9                 1 * 13-NAND                  74LS133
UE1                 1K*4 RAM                     MM2114-3
UE2                 1K*4 RAM                     MM2114-3
UE8                 8-bit buffer                 65245
UE10                CPU                          6502
UE11     C000-EFFF  BASIC ROM                    901486-01
UE12     E000-FFFF  KERNAL ROM                   901486-07
UF8                 8-bit buffer                 65245
U13                 4 * 2-AND                    74LS08
U14                 2K*8 RAM                     HM6116-4
U15                 2K*8 RAM                     HM6116-4

The above is not complete, I am thinking about giving each RAM IC its own
range.
Another question: as you can see, both are D-revisions. Do other revisions
exist?

Groetjes, Ruud

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