Simulating the download of a sector from the PICO to the SDRAM

SIMULATING THE SPI TRAFFIC THAT WOULD COME FROM THE PICO SOFTWARE

The software opens the virtual cartridge file on microSD card and reads through it, sending the words down to the FPGA using SPI messages. Each word is pushed using two SPI x06 messages, each transporting 8 bits of the word over the link. It produces the intended RAM address and pushes it over SPI before each sector, thus using three x05 messages. 

An entire sector is written with three x05 and 642 x06 messages. I simulated a download of one sector, again using cylinder 1, head 1 and sector 1 to validate the address generation, however I didn't write all 321 words since the first few is enough to ensure the logic is working. This worked perfectly.

I then simulated an upload from the same location, which I did by issuing three x05 to set the address and then pairs of x88 to read the data. It gave me the proper data.