Simulating capturing a write to the Virtual 2315 Cartridge Facility

WRITING TO THE DISK FROM 1130 INVOLVES SIGNALS ORIGINATING IN THE DRIVE

The disk drive generates a 720KHz signal which defines the bit cells that will be written onto the platter. This signal is passed to the IBM 1130 controller logic which uses it to gate signals out a combined clock and data write line. When the bit cell is in the first half (clock) the 1130 always emits a 1 value, while in the second half of the bit cell we emit either 1 or 0 depending on the bit value encoded in that bit cell. 

USED PREVIOUSLY DEVELOPED LOGIC TO SIMULATE THE COMBINED CLK + DATA LINE

I had developed macros and logic to simulate the output from the controller as it wrote a sector to the drive. I used this as input to my design, triggering it to command a write at sector 1 of head 1 of cylinder 1. The data was decoded and written to SDRAM at the correct addresses, exactly as desired. 

NEXT - GENERATE THE FPGA LOGIC AND DOWNLOAD ONTO THE RK-05 EMULATOR

Next up I should shift over to the Lattice toolchain to generate the FPGA bitstream and load it to the RK-05 Emulator hardware that I am leveraging for this virtual disk drive. A similar generation must be done for the C code that runs on the Raspberry Pi Pico inside the RK-05 Emulator, then update the Pico. That enables the start of live testing on an IBM 1130 with its internal disk drive.