title Spoonfeeding the 6809 over the CoCo cartridge connector, or, Why I don't need any ROM
user strick
ip 24.125.136.69
vol 1
lock ********

/imagefile -o PXL_20240225_170448051.jpg

 


/imagefile -o PXL_20240225_171946128.jpg

 


/imagefile -o PXL_20240225_170619485.jpg

 

/imagefile -o PXL_20240225_170834885.jpg

 


/imagefile -o PXL_20240225_171015357.jpg

 

/imagefile -o PXL_20240225_172233462.jpg



Firmware:  https://github.com/strickyak/spoonfeeder/blob/main/micropy/step5.py

Hardware cartridge:  https://github.com/strickyak/spoonfeeder/tree/main/v1

This is what HALT/, E, A0, and R/W look like when HALT/ has been held down but is released and the 6809 starts executing instructions again:

/imagefile -xl PXL_20240215_060736565.jpg

This is spoon-feeding 2 instructions (6 bytes).  The top signal is a debugging output to show the 6 fetch cycles being spoonfed.  Then E, A0, and R/W.  You can see R/W relax to a middle voltage when the CPU is Halted by HALT/.

/imagefile -xl PXL_20240215_080302529.jpg

My board in a Coco2 with the Pico W powered and oscilloscope probes.

/imagefile -xl PXL_20240215_081145144.jpg

The first two bytes I ever spoon fed:  'X' and 'Y' in the first to screen positions at addresses $0000 and $0001.

/imagefile -xl PXL_20240215_080316848.jpg

My circuit board.  The middle and right are my hand-routing.  The left came with the Prototyping board I based it on (  https://raw.githubusercontent.com/JayesonLS/TandyCircuitsAndLogic/master/CoCoProtoBoard/CoCoProtoBoard.png )

/imagefile -xl PXL_20240206_224027