Thursday, January 19, 2017

Setting up emulator role testbed and building out test mechanisms


I am using a short breakout board from Digilent to give me access to all forty of the IO pins that exist on the FX2 connector of the fpga. I use these 40 pins to drive outputs and receive inputs from the Alto (or the Diablo for driver mode), with the custom PCBs I made used to convert voltages between 3.3 and 5V, provides terminator and pull-up resistances, and drive outputs with over 100ma apiece.

Short breakouit board

FPGA board

I don't need 5V nor the high current support for my testing, thus the short board allows me to wire up the input and output signals to the other IO pins of the FPGA so that I can drive my logic within the same board.

The PMOD connectors support 28 such signals (plus 4 that are shared with LEDs). Since I only use 15 input and 12 output signals for the emulator, the 28 PMOD signals are sufficient to driver/check all the signals.

I spent the day assigning the PMOD pins for each of the active input and output pins on the FX2, but didn't wire it up because I will be bringing the FPGA board to the Alto session tomorrow to do the archiving and other work. However, with the assignments known, wiring will be quick and I can set up all the test mechanisms that will drive the testing.

Tomorrow we will use the disk tool to archive all the cartridges on hand, then write over the previously erased cartridge to give us the 'games' archive image with a plethora of games that were used on Altos. 


  1. Carl... where have you gone?



  2. Hi Bob

    Several different distractions arose in the past weeks, including a minor health issue but mostly obligations that kept me from any work or posting. I am back in the saddle and just posted again a few minutes ago