home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Rockford Magazine
/
Rockford_Magazine_033_19xx_-_de_Disk_3_of_5_Side_B.d64
/
15.0
< prev
next >
Wrap
Text File
|
2023-02-26
|
11KB
|
235 lines
Path: crl2.crl.com!not-for-mail
From: ceejack@crl.com (Jack Vander White)
Newsgroups: comp.sys.cbm
Subject: VIC-20 Info
Date: 31 Jul 1995 11:11:36 -0700
Organization: Humanity Against Late-Night Infomercials
Message-ID: <3vj6co$7d4@crl2.crl.com>
NNTP-Posting-Host: crl2.crl.com
X-Newsreader: TIN [version 1.2 PL2]
Posted to comp.sys.cbm by request of the author.
======================
= =
= Inside your Vic 20 =
= By Ward Shrake =
= =
======================
This document is a collection of pinout diagrams and technical notes, meant
to assist anyone who wishes to experiment electronically with the "obsolete"
Commodore Vic20 computer. Specifically, this document addresses the cartridge
or Memory Expansion port and related items, such as ROM & EPROM memory chips.
This is a very preliminary version of a document which could be expanded, if
I decide to go even more ballistic, later on. All this text was written out in
one day, with no prior planning, so if its a little jumpy, that's why. Later
versions should be better. Right now, probably anything helps, so here it is.
(Additions, corrections or whatever can be sent via email to the author.)
Ward Shrake, July 1995
email: wardshrake@aol.com
----------------------------------------------------------------------------
Pinout diagram #1: Memory Expansion port connector of the Vic20 computer
----------------------------------------------------------------------------
Below is the pinout diagram of the Vic20 cartridge port, or Memory Expansion
Connector. Please note that this is NOT the pinout for a cartridge that might
fit into any port, nor is it a pinout of the User Port, which is something
completely different. This diagram shows the cartridge port's pinout, as you
face the rear of the Vic 20 computer. (The port is on the Vic20's left side.)
Bottom side of expansion port. Top side of expansion port.
(This half is on bottom.) (This half is towards the keyboard.)
(This edge of the connector faces left,
where the power switch and the LED are.)
{$7d} {$7d}
GND A {$7d} {$7d} {$7d} {$7d} 1 GND
CA0 B {$7d} {$7d} {$7d} {$7d} 2 CD0
CA1 C {$7d} {$7d} {$7d} {$7d} 3 CD1
CA2 D {$7d} {$7d} {$7d} {$7d} 4 CD2
CA3 E {$7d} {$7d} {$7d} {$7d} 5 CD3
CA4 F {$7d} {$7d} {$7d} {$7d} 6 CD4
CA5 H {$7d} {$7d} {$7d} {$7d} 7 CD5
CA6 J {$7d} {$7d} {$7d} {$7d} 8 CD6
CA7 K {$7d} {$7d} {$7d} {$7d} 9 CD7 (Memory Location:)
CA8 L {$7d} {$7d} {$7d} {$7d} 10 BLK 1 ($2000 - $3fff)
CA9 M {$7d} {$7d} {$7d} {$7d} 11 BLK 2 ($4000 - $5fff)
CA10 N {$7d} {$7d} {$7d} {$7d} 12 BLK 3 ($6000 - $7fff)
CA11 P {$7d} {$7d} {$7d} {$7d} 13 BLK 5 ($a000 - $bfff)
CA12 R {$7d} {$7d} {$7d} {$7d} 14 RAM 1 ($0400 - $07ff)
CA13 S {$7d} {$7d} {$7d} {$7d} 15 RAM 2 ($0800 - $0bff)
I/O 2 T {$7d} {$7d} {$7d} {$7d} 16 RAM 3 ($0c00 - $0fff)
I/O 3 U {$7d} {$7d} {$7d} {$7d} 17 V R/W
S02 V {$7d} {$7d} {$7d} {$7d} 18 C R/W
NMI W {$7d} {$7d} {$7d} {$7d} 19 IRQ
RESET X {$7d} {$7d} {$7d} {$7d} 20 NC
NC Y {$7d} {$7d} {$7d} {$7d} 21 +5 Volts
GND Z {$7d} {$7d} {$7d} {$7d} 22 GND
{$7d} --- {$7d}
---------
(This edge of the connector is on the
right, where all the other ports are.)
Pinout Notes:
-------------
BLKxx = 8K decoded RAM/ROM block xx, active low. See chart above for area.
CAxx = Address bus line xx
CDxx = Data bus line xx
C R/W = Read/Write line from CPU. (Read = high, Write = low)
GND = System ground
I/O 2 = Decoded I/O block 2, starting at $9130
I/O 3 = Decoded I/O block 3, starting at $9140
IRQ = 6502 Interrupt Request line (active low)
NC = No connection
NMI = 6502 Non-Maskable Interrupt line (active low)
RAMxx = 1K decoded RAM blockxx, active low. See chart above for memory area.
RESET = 6502 reset line (active low)
S02 = Phase 2 system clock
V R/W = Read/Write line from Vic chip. (Read = high, Write = low)
-----------------------------------------------------------------------
Pinout diagram #2: A standard Vic20 cartridge's card edge connector
-----------------------------------------------------------------------
Below is a pinout diagram of a standard Vic20 cartridge, seen facing its card
edge connector. Please note that this is NOT the pinout of the port it plugs
into, which is shown above. The two pinouts are exact opposites, because you
are facing the port head-on as is, but you have to flip a cartridge around
180 degrees to be able to look at it head-on, facing its card edge connector.
Bottom side of cartridge Top (label or component) side of cartridge
-
GND Z {$7d} {$7d} 22 GND
NC Y {$7d} {$7d} 21 +5 Volts
RESET X {$7d} {$7d} 20 NC
NMI W {$7d} {$7d} 19 IRQ
S02 V {$7d} {$7d} 18 C R/W
I/O 3 U {$7d} {$7d} 17 V R/W (Memory location:)
I/O 2 T {$7d} {$7d} 16 RAM 3 ($0c00 - $0fff)
CA13 S {$7d} {$7d} 15 RAM 2 ($0800 - $0bff)
CA12 R {$7d} {$7d} 14 RAM 1 ($0400 - $07ff)
CA11 P {$7d} {$7d} 13 BLK 5 ($a000 - $bfff)
CA10 N {$7d} {$7d} 12 BLK 3 ($6000 - $7fff)
CA9 M {$7d} {$7d} 11 BLK 2 ($4000 - $5fff)
CA8 L {$7d} {$7d} 10 BLK 1 ($2000 - $3fff)
CA7 K {$7d} {$7d} 9 CD7
CA6 J {$7d} {$7d} 8 CD6
CA5 H {$7d} {$7d} 7 CD5
CA4 F {$7d} {$7d} 6 CD4
CA3 E {$7d} {$7d} 5 CD3
CA2 D {$7d} {$7d} 4 CD2
CA1 C {$7d} {$7d} 3 CD1
CA0 B {$7d} {$7d} 2 CD0
GND A {$7d} {$7d} 1 GND
--
--------------------------------------------------
Pinout diagram #3: EPROM # 2764A
(This is a standard, 8K x 8 bit memory chip)
--------------------------------------------------
{$7d} !! {$7d}
Vpp {$7d} 1 28 {$7d} Vcc (+5 Volts)
A12 {$7d} 2 27 {$7d} PGM (Active low)
A7 {$7d} 3 26 {$7d} N.C. (No connection)
A6 {$7d} 4 25 {$7d} A8
A5 {$7d} 5 24 {$7d} A9
A4 {$7d} 6 23 {$7d} A11
A3 {$7d} 7 22 {$7d} OE (Output Enable; Active low)
A2 {$7d} 8 21 {$7d} A10
A1 {$7d} 9 20 {$7d} CE (Chip Enable; Active low)
A0 {$7d} 10 19 {$7d} D7
D0 {$7d} 11 18 {$7d} D6
D1 {$7d} 12 17 {$7d} D5
D2 {$7d} 13 16 {$7d} D4
GND {$7d} 14 15 {$7d} D3
{$7d}{$7d}
See Note 6 below, for some tips on using this as a replacement memory
chip, on a modified cartridge body, for experimentation purposes. Note
that there are differences between it and the standard Vic20 chip below,
that will have to be accounted for before it can be wired to the boards.
--------------------------------------------------------
Pinout diagram #4: "MPS 2364" ROM chip
(Commodore-standard, 24-pin ROM chip, 8K x 8 bit.)
--------------------------------------------------------
{$7d} !! {$7d}
CA7 {$7d} 1 24 {$7d} +5 Volts
CA6 {$7d} 2 23 {$7d} CA8
CA5 {$7d} 3 22 {$7d} CA9
CA4 {$7d} 4 21 {$7d} CA12
CA3 {$7d} 5 20 {$7d} CS (Chip select, active low)
CA2 {$7d} 6 19 {$7d} CA10
CA1 {$7d} 7 18 {$7d} CA11
CA0 {$7d} 8 17 {$7d} CD7
CD0 {$7d} 9 16 {$7d} CD6
CD1 {$7d} 10 15 {$7d} CD5
CD2 {$7d} 11 14 {$7d} CD4
GND {$7d} 12 13 {$7d} CD3
{$7d}{$7d}
This pinout was derived from a Vic20 schematic, found in the book the
"Vic20 Programmer's Reference Guide". (Great book!) Please note that while
this is an 8k-by-8-bit Commodore memory chip (its actually the Kernal chip,
located at $E000-$FFFF), and that while it could normally be assumed safely
that a company would standardize and use the same chips in their cartridges
that they used in their computer's motherboards, this is Commodore we're
talking about. A bit of paranoia might be in order. Having said that, I'll
note that as of this writing, the author has not compared this diagram and
an actual memory chip from a Commodore-produced Vic20 cartridge. 'Nuff said!
---------------------------------------------------------------------------
Assorted notes on the diagrams above, and related subjects. (No order.)
---------------------------------------------------------------------------
Note 1: Information for the diagrams above was taken from the Vic20 reference
book "The Vic Revealed" by Nick Hampshire, 1982, Hayden Book Co, Inc.
That info was verified by checking it against information found in
the "Vic20 Programmer's Reference Guide," 1982, by Commodore Business
Machines, Inc. and Howard W. Sams & Company, Inc.
Note 2: You are looking at the cart pinout as if you were holding an unopened
cartridge, label-side up (or right, in these diagrams) with the gold
fingers pointing at you. If you are looking at a bare circuit board
once it has been taken out of its outer plastic case, the chip is on
top (or right, as shown here) again with the gold fingers facing you.
(The diagrams were drawn sideways, as the ASCII drawings are somewhat
clearer this way, believe it or not. There is less confusion this way
over which pin is which. Horizontally, each name takes up more space.)
Note 3: Radio Shack currently (as of July 1995) carries a part that works as
a Memory Expansion Port connector for the Vic20. However, they are
discontinuing it, and are selling off all remaining stock. Their part
number is 276-1551 for their "44-position card-edge connector." Once
these are gone, you'll have to find another source for them. ($1.27)
This part is useful for experimenting with this port on the Vic20, as
it is a perfect fit, as is, to accept standard plug-in Vic cartridges.
Note 4: A perhaps useful experimenter's tip: If you plan to take the circuit
board out of the cartridge case, then remove the ROM chip(s) from the
circuit board, mark the two sides of the board first, or you may no