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Index
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Model:
Commodore Plus/4
Release Date:
1984
Original Price:
$300
Processor:
MOS Technology 7501 1.76 MHz
Memory:
64 KB RAM / 32 KB ROM
Alas, yet another example of youthful indiscretion ( ie. I got rid of it )
I can't believe I found one of these - brand new still in the original box
at the Thrift Store for SIX BUCKS!
A predecessor to the popular C64, the "Plus/4" moniker refers to the built-in office
suite including word processor, spreadsheet, database and graphing applications. It
was only produced for one year, being discontinued in 1985. One of the main reasons
for this was the incompatibility with the C64. Not only were the Atari-style
joysticks no longer supported, instead using an 8-pin mini-DIN connector, the
expansion port was changed as was the cassette tape interface. "Upgrading" to the
Plus/4 required purchasing all new peripherals as well as the base system.
One available option was a high-speed parallel floppy disk drive (the Commodore 1551),
which came with a parallel interface that plugged into the expansion port.
>>
Click here to download the Service Manual (3.04 mb)
>>
Click here to download extensive technical documentation (76.2 mb)
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Pinouts:
8-pin DIN Video
Pin 1 --> Luminance
Pin 2 --- Ground
Pin 3 --> Audio Out
Pin 4 --> Composite Video Out
Pin 5 <-- Audio In
Pin 6 --> Chroma
Pin 7 ... n/c
Pin 8 ... n/c
Controller Ports
Pin 1 <-- [JOYA0] [JOYB0]
Pin 2 <-- [JOYA1] [JOYB1]
Pin 3 <-- [JOYA2] [JOYB2]
Pin 4 <-- [JOYA3] [JOYB3]
Pin 5 --> +5vdc
Pin 6 <-- [Button A] [Button B]
Pin 7 --> GND
Pin 8 ... ???
| User Expansion Port |
 |
| Pin 01 = GND | Pin 13 = GND |
| Pin 02 = +5vdc (100 mA max) | Pin 14 = D0 |
| Pin 03 = /RESET | Pin 15 = RxD |
| Pin 04 = D2/Cassette Sense | Pin 16 = RTS |
| Pin 05 = D3 | Pin 17 = DTR |
| Pin 06 = D4 | Pin 18 = D7 |
| Pin 07 = D5 | Pin 19 = DCD |
| Pin 08 = Receive Clock | Pin 20 = D6 |
| Pin 09 = ATN | Pin 21 = CTS |
| Pin 10 = +9vac (+ phase) | Pin 22 = DSR |
| Pin 11 = +9vac (- phase) | Pin 23 = TxD |
| Pin 12 = GND | Pin 24 = GND |
Serial I/O
Pin 1 <-- Serial SRQIN
Pin 2 --- Ground
Pin 3 <-> Serial ATN
Pin 4 <-> Serial CLK
Pin 5 <-> Serial DATA
Pin 6 <-> Reset
Cassette Interface
Pin 1 --- GND
Pin 2 --> +5vdc
Pin 3 --> Motor
Pin 4 <-- Read
Pin 5 --> Write
Pin 6 --> Sense
Pin 7 --- GND
| Cartridge Expansion Port |
 |
| Pin 01 = GND | Pin 26 = GND |
| Pin 02 = +5vdc | Pin 27 = /C1Low |
| Pin 03 = +5vdc | Pin 28 = /RESET |
| Pin 04 = /IRQ | Pin 29 = /RowAddressStrobe |
| Pin 05 = R/W | Pin 30 = ArtificialPi0 |
| Pin 06 = C1High | Pin 31 = A15 |
| Pin 07 = C2Low | Pin 32 = A14 |
| Pin 08 = C2High | Pin 33 = A13 |
| Pin 09 = /ChipSelect1 | Pin 34 = A12 |
| Pin 10 = /ChipSelect0 | Pin 35 = A11 |
| Pin 11 = /ColumnAddressStrobe | Pin 36 = A10 |
| Pin 12 = MUX | Pin 37 = A9 |
| Pin 13 = BusAvailabale | Pin 38 = A8 |
| Pin 14 = D7 | Pin 39 = A7 |
| Pin 15 = D6 | Pin 40 = A6 |
| Pin 16 = D5 | Pin 41 = A5 |
| Pin 17 = D4 | Pin 42 = A4 |
| Pin 18 = D3 | Pin 43 = A3 |
| Pin 19 = D2 | Pin 44 = A2 |
| Pin 20 = D1 | Pin 45 = A1 |
| Pin 21 = D0 | Pin 46 = A0 |
| Pin 22 = AddressEnableCode | Pin 47 = n/c |
| Pin 23 = ExternalAudioIn | Pin 48 = n/c |
| Pin 24 = ArtificialPhi2 | Pin 49 = n/c |
| Pin 25 = GND | Pin 50 = GND |
Power
Pin 1 <-- 9vac
Pin 2 <-- +5vdc
Pin 3 <-- 9vac
Pin 4 --- GND
All Pin-Outs Are Courtesy of
the Hardware Book Project
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Commodore