Hi all,
I’m trying to access the Furby’s 80 K ROM onboard the SPC81A. I’m utilizing an Arduino Nano in this process. A rough pinout of the Furby’s SPC81A daughter board can be found
here. Note the memory map on page 5.
As stated
elsewhere, the SPC81A is a RISC 6502. It contains a little less than half of the opcodes found on an actual 6502, although I am unsure which ones are omitted. The datasheet for the SPC81A can be found
here.
The SPC81A daughter board has 25 pins. My implementation uses pins 14 (Serial Data In), 17 (Serial Data Out), and 18 (Serial Clock). I’m assuming I can send commands to the processor through these ports, but I really have no idea of knowing.
Here is an outline of how I’d like to retrieve the contents of the 80k ROM:
1) Send command $4C (JMP) to set the address to $00000
2) Load contents of address to the accumulator using $A9 (LDA)
3) Send contents of the accumulator to the serial line
4) Output to Arduino serial monitor
5) Increment address by 1
6) Repeat until address $17FFF is reached
Note that between each bit, the clock will go high or low. (bit 1, send clock high, bit 2, send clock low, bit 3, send clock high, etc)
I’ve never messed with a 6502 before, so any advice here would be welcome.