Simulating Virtual 2315 Cartridge Facility doing a read

MUST SIMULATE CONTROLLER, DISK AND THE PICO LOADING SDRAM CONTENT

Another layer of complexity was added here as I must set up the SDRAM contents if I am going to verify that an attempt by the controller logic to read a sector receives the data properly. As I wish to verify the RAM addresses being generated, I can't just read the first sector as that has cylinder, head and sector values of zero. 

The Raspberry Pi PICO reads the virtual cartridge image from the microSD card and pushes the contents over SPI to the FPGA, which writes them in the SDRAM. This involves 643 SPI messages which I can simulate because of my macros. If I see that the proper data is being written to SDRAM addresses to match the intended sector, that would be sufficient for the test. 

My SDRAM simulation can pull data from a text file which I preload with the contents that represent the sector. The file must be large enough to get to cylinder 1, head 1 and sector 1 at least in order to have non-zero values for these fields that make up the RAM address. This requires 4,494 lines in the file to cover 321 words for each of 14 sectors, but due to the sparse addressing scheme of the SDRAM that sector starts at word 6656 and ends at 6977 thus the file is larger. 

I used a Python program to generate the file and stored values that correspond to the sector and word so that I can easily tell if the correct word is fetched at any time. 

RESULTS WERE GOOD - THE DATA BEING EMITTED IS WHAT I PUT IN TEXT FILE

I did see the program receive the values 1A00 to 1B40 which are the ones in the file corresponding to that sector. Further, the clock and data pulses generated by my design and sent to the IBM 1130 controller logic were correct for those values. 

EXAMINING PROPER ADDRESS TO SDRAM

Looking at the values used in the SDRAM controller module, it was reading from the intended addresses 1A00 to 1B40 just as it should. It is time to turn my attention to simulating a sector write from the 1130 and ensure that I capture the data properly and store it in the intended RAM locations.