Previously I connected up the 6502, now it was time to get the CPU to actually do something so I connected some LEDs to a couple of the address bus (pins 9- 13). I powered both circuits using a couple of AA batteries, success the LEDs started to blink randomly.
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| W65C02 Pinout |
Enough of the randomness I actually wanted the CPU to do something. I hardwired the data bus so the CPU would be forced to run the same instruction over and over, the NOP or No operation instruction was a good choice. This does nothing for 2 clock cycles, usually used to time a delay or fill patches in a program.
| Pin | Data Bus | Connection |
|---|---|---|
| 26 | D7 | +5v (1) |
| 27 | D6 | +5v (1) |
| 28 | D5 | +5v (1) |
| 29 | D4 | 0V (0) |
| 30 | D3 | +5v (1) |
| 31 | D2 | 0V (0) |
| 32 | D1 | +5v (1) |
| 33 | D0 | 0V (0) |
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| Updated breadboard with the NOP / 11101010 hardwired to the 8 data pins |
So I had basically made some blinkenlights, exciting times. Watching the LEDs connected to the address bus count in a binary was quite therapeutic.
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| Arduino Mega monitoring the address and data buses |
In the first part of Ben Eater's 6502 videos he connected up a Arduino Mega to the address and data buses and wrote a little Arduino sketch to monitor these.