I wrote these programs to test the RAM, ROM and PLA chips with an Arduino Uno because I don't own a second known-working C64 to test them on.
With the help of these sketches I found my CHAROM and PLA were fried. I also was able to find that one of the chips in my International Soccer cartridge was failing to obey the /CS signal. If you are trying to repair your C64, I hope they help you too and wish you good luck!
Some sketches work on an Arduino Uno. Some others require an Arduino MEGA (I actually got a Robotdyn Mega Pro 2560, which is a pin-compatible, smaller factor version of the real Mega). The Arduino MEGA has plenty of pins and makes it easier to test the chips and also provide meaningful information through the serial port.
Check the chips for electrical consistence before wiring, ie: inputs are not shorted, chip obeys /CS, etc.
See test details on each sketch's heading comments.
Summary of 64K x 1 bit RAM test
Test for the 64K x 1 bit chips on long board breadbin C64s and older C64Cs (there are eight of these chips for a total 64 x 8 Kbit).
+-----+
+----[PWR]-------------------| USB |--+
| +-----+ |
| GND/RST2 [ ][ ] |
| MOSI2/SCK2 [ ][ ] A5/SCL[ ] | C5
| 5V/MISO2 [ ][ ] A4/SDA[ ] | C4
| AREF[ ] |
| GND[ ] |
| [ ]N/C SCK/13[ ] | B5
| [ ]IOREF MISO/12[ ] | B4 --- DRAM DIN
| [ ]RST MOSI/11[ ]~| B3 --- DRAM /WE
| [ ]3V3 +---+ 10[ ]~| B2 --- DRAM /RAS
| [ ]5v -| A |- 9[ ]~| B1 --- DRAM /CAS
| [ ]GND -| R |- 8[ ] | B0 --- RAM DOUT
| [ ]GND -| D |- |
| [ ]Vin -| U |- 7[ ] | D7 --- RAM A7
| -| I |- 6[ ]~| .
C0 | [ ]A0 -| N |- 5[ ]~| .
C1 | [ ]A1 -| O |- 4[ ] | .
C2 | [ ]A2 +---+ INT1/3[ ]~| .
C3 | [ ]A3 INT0/2[ ] | .
C4 | [ ]A4/SDA RST SCK MISO TX>1[ ] | .
C5 | [ ]A5/SCL [ ] [ ] [ ] RX<0[ ] | D0 --- RAM A0
| [ ] [ ] [ ] |
| UNO_R3 GND MOSI 5V ____________/
\_______________________/
- LED (pin 13) off: TEST PASS
- LED (pin 13) on: TEST FAIL (will turn back off at the end of the test cycle, so PAY ATTENTION)
Summary of 64K x 4 bit RAM test (Arduino MEGA)
Test for the 64K x 4 bit chips on short board C64Cs (TMS 4464, NEC 41464, etc). There are two of these chips on these boards.
The diagram is for a Robotdyn Mega Pro 2560 (smaller factor Arduino Mega clone).
Also works with a real Arduino Mega, just pay attention to the different pin layout.
+---------------
| VIN[ ][ ]VIN \
| GND[ ][ ]GND /
| 5V[ ][ ]5V \
| 3V3[ ][ ]3V3 /
| RST[ ][ ]AREF \
E1 | TX[ ][ ]RX / E0
E5 | D3[ ][ ]D2 \ E4
E3 | D5[ ][ ]D4 / G5
H4 | D7[ ][ ]D6 \ H3
H6 | D9[ ][ ]D8 / H5
B5 | D11[ ][ ]D10 \ B4
B7 | D13[ ][ ]D12 / B6
J0 | D15[ ][ ]D14 \ J1
H0 | D17[ ][ ]D16 / H1
D2 | D19[ ][ ]D18 \ D3
D0 | D21[ ][ ]D20 / D1
RAM A1 --- A1 | D23[ ][ ]D22 \ A0 --- RAM A0
RAM A3 --- A3 | D25[ ][ ]D24 / A2 --- RAM A2
RAM A5 --- A5 | D27[ ][ ]D26 \ A4 --- RAM A5
RAM A7 --- A7 | D29[ ][ ]D28 / A6 --- RAM A7
C6 | D31[ ][ ]D30 \ C7
+----------------
--+-----+-------+
\ | | |
/ | USB | [RST] |
\ +-----+ |
/ |
\ |
RAM IO2 --- F1 / A1[ ][ ]A0 | F0 --- RAM IO1
RAM IO4 --- F3 \ A3[ ][ ]A2 | F2 --- RAM IO3
F5 / A5[ ][ ]A4 | F4
F7 \ A7[ ][ ]A6 | F6
K1 / A9[ ][ ]A8 | K0
K3 \ A11[ ][ ]A10 | K2
K5 / A13[ ][ ]A12 | K4
K7 \ A15[ ][ ]A14 | K6
C4 / D33[ ][ ]D32 | C5
RAM /RAS --- C2 \ D35[ ][ ]D34 | C3 --- RAM /CAS
RAM /OE --- C0 / D37[ ][ ]D36 | C1 --- RAM /WE
G2 \ D39[ ][ ]D38 | D7
G0 / D41[ ][ ]D40 | G1
L6 \ D43[ ][ ]D42 | L7
L4 / D45[ ][ ]D44 | L5
L2 \ D47[ ][ ]D46 | L3
---------------+
Sample serial output (115200 bps):
1111... PASS
0000... PASS
0101... PASS
1010... PASS
1111... PASS
0000... PASS
Summary of ROM test
+-----+
+----[PWR]-------------------| USB |--+
| +-----+ |
| GND/RST2 [ ][ ] |
| MOSI2/SCK2 [ ][ ] A5/SCL[ ] | C5
| 5V/MISO2 [ ][ ] A4/SDA[ ] | C4
| AREF[ ] |
| GND[ ] |
| [ ]N/C SCK/13[ ] | B5 --- ROM O8
| [ ]IOREF MISO/12[ ] | B4 --- ROM O7
| [ ]RST MOSI/11[ ]~| B3 --- ROM A11
| [ ]3V3 +---+ 10[ ]~| B2 --- ROM A10
| [ ]5v -| A |- 9[ ]~| B1 --- ROM A9
| [ ]GND -| R |- 8[ ] | B0 --- ROM A8
| [ ]GND -| D |- |
| [ ]Vin -| U |- 7[ ] | D7 --- ROM A7
| -| I |- 6[ ]~| .
ROM O1 --- C0 | [ ]A0 -| N |- 5[ ]~| .
ROM O2 --- C1 | [ ]A1 -| O |- 4[ ] | .
ROM O3 --- C2 | [ ]A2 +---+ INT1/3[ ]~| .
ROM O4 --- C3 | [ ]A3 INT0/2[ ] | .
ROM O5 --- C4 | [ ]A4/SDA RST SCK MISO TX>1[ ] | .
ROM O6 --- C5 | [ ]A5/SCL [ ] [ ] [ ] RX<0[ ] | D0 --- ROM A0
| [ ] [ ] [ ] |
| UNO_R3 GND MOSI 5V ____________/
\_______________________/
- Random activity on LED (pin 13): TEST PASS
- LED is stuck either on or off: TEST FAIL
Summary of PLA test
+-----+
+----[PWR]-------------------| USB |--+
| +-----+ |
| GND/RST2 [ ][ ] |
| MOSI2/SCK2 [ ][ ] A5/SCL[ ] | C5
| 5V/MISO2 [ ][ ] A4/SDA[ ] | C4
| AREF[ ] |
| GND[ ] |
| [ ]N/C SCK/13[ ] | B5 --- PLA I13
| [ ]IOREF MISO/12[ ] | B4 --- PLA I12
| [ ]RST MOSI/11[ ]~| B3 --- PLA I11
| [ ]3V3 +---+ 10[ ]~| B2 --- PLA I10
| [ ]5v -| A |- 9[ ]~| B1 --- PLA I9
| [ ]GND -| R |- 8[ ] | B0 --- PLA I8
| [ ]GND -| D |- |
| [ ]Vin -| U |- 7[ ] | D7 --- PLA I7
| -| I |- 6[ ]~| .
PLA I14 --- C0 | [ ]A0 -| N |- 5[ ]~| .
PLA I15 --- C1 | [ ]A1 -| O |- 4[ ] | .
PLA F0/4 --- C2 | [ ]A2 +---+ INT1/3[ ]~| .
PLA F1/5 --- C3 | [ ]A3 INT0/2[ ] | .
PLA F2/6 --- C4 | [ ]A4/SDA RST SCK MISO TX>1[ ] | .
PLA F3/7 --- C5 | [ ]A5/SCL [ ] [ ] [ ] RX<0[ ] | D0 --- PLA I0
| [ ] [ ] [ ] |
| UNO_R3 GND MOSI 5V ____________/
\_______________________/
- Random activity on LED (pin 13): TEST PASS
- A series of n LED flashes: TEST FAIL output Fn-1
Summary of ROM dump (Arduino MEGA)
The diagram is for a Robotdyn Mega Pro 2560 (smaller factor Arduino Mega clone).
Also works with a real Arduino Mega, just pay attention to the different pin layout.
This is for 2364 (8 KB) ROMs commonly used for cartridges, BASIC and KERNAL ROMs. See sketch comments for 2332 (4 KB) ROMs.
+---------------
| VIN[ ][ ]VIN \
| GND[ ][ ]GND /
| 5V[ ][ ]5V \
| 3V3[ ][ ]3V3 /
| RST[ ][ ]AREF \
E1 | TX[ ][ ]RX / E0
E5 | D3[ ][ ]D2 \ E4
E3 | D5[ ][ ]D4 / G5
H4 | D7[ ][ ]D6 \ H3
H6 | D9[ ][ ]D8 / H5
B5 | D11[ ][ ]D10 \ B4
B7 | D13[ ][ ]D12 / B6
J0 | D15[ ][ ]D14 \ J1
H0 | D17[ ][ ]D16 / H1
D2 | D19[ ][ ]D18 \ D3
D0 | D21[ ][ ]D20 / D1
ROM A1 --- A1 | D23[ ][ ]D22 \ A0 --- ROM A0
ROM A3 --- A3 | D25[ ][ ]D24 / A2 --- ROM A2
ROM A5 --- A5 | D27[ ][ ]D26 \ A4 --- ROM A5
ROM A7 --- A7 | D29[ ][ ]D28 / A6 --- ROM A7
C6 | D31[ ][ ]D30 \ C7
+----------------
--+-----+-------+
\ | | |
/ | USB | [RST] |
\ +-----+ |
/ |
\ |
ROM D1 --- F1 / A1[ ][ ]A0 | F0 --- ROM D0
ROM D3 --- F3 \ A3[ ][ ]A2 | F2 --- ROM D2
ROM D5 --- F5 / A5[ ][ ]A4 | F4 --- ROM D4
ROM D7 --- F7 \ A7[ ][ ]A6 | F6 --- ROM D6
K1 / A9[ ][ ]A8 | K0
K3 \ A11[ ][ ]A10 | K2
K5 / A13[ ][ ]A12 | K4
K7 \ A15[ ][ ]A14 | K6
ROM A11 --- C4 / D33[ ][ ]D32 | C5 --- ROM A12
ROM A9 --- C2 \ D35[ ][ ]D34 | C3 --- ROM A10
ROM A8 --- C0 / D37[ ][ ]D36 | C1 --- ROM A9
G2 \ D39[ ][ ]D38 | D7
ROM /CE --- G0 / D41[ ][ ]D40 | G1
L6 \ D43[ ][ ]D42 | L7
L4 / D45[ ][ ]D44 | L5
L2 \ D47[ ][ ]D46 | L3
---------------+
The program will prompt whether you want to drive /CE low or high and then dump the ROM over to the serial port (115.2 Kbps).
Driving /CE low enables the chip and produces a hex dump you can convert to bin with xxd -r <dump.txt >dump.bin:
/CE high or low? [h/l] l
00000000: 27 80 a8 80 c3 c2 cd 38 30 00 40 c0 40 c0 40 c0
00000010: 40 c0 40 c0 40 c0 40 c0 00 80 80 10 10 10 10 20
...
Driving /CE high disables the chip and should read ff throughout the entire dump:
/CE high or low? [h/l] h
00000000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
00000010: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
...
A valid dump with /CE high means the chip FAILS to obey the /CE line.
- Zimmers invaluable archive of pinouts, schematics and documents
- ~rcarlsen archive
- PLA C code equations
- Commodore 64: how to repair it, step by step
- Arduino ASCII diagrams
- ... and Commodore Business Machines for making the BEST COMPUTER EVER