Gigatron Hackers

First excuse me for my long time out of the forum. I'm not planning to sell any kit for the ROM emulator, but the layout files are freely available and there are many prototype makers around for the PCB (I ordered the boards to www.pcbway.com). The components are SMD and they may look difficult to s...

A few terminal captures, using 'minicom -c on'

Hi, A first working version of the ROM emulator firmware is attached here. ISRDfirmware.zip It requires an ANSI serial terminal program like "minicom" (linux) or Hyperterminal (windows, not tested). And the program "lpc21isp" for loading the firmware into the microcontroller. Reg...

It was hard to achieve, but I finally can run the ROM emulator at full speed (6.25MHz) with breakpoints enabled. I had to use a NOP op-code for breakpoints because these instructions are executed before stopping the clock. This gives me an extra 8 ARM cycles to disable the PWM wave of clock, and the...

The (vPC_low-2) was the problem. Thanks a lot!

I'll keep the stack pointer reset because it can have any value when the Gigatron stops and I'd like to get all the possible stack space for the GT1 program.

Hi, I'm trying to use the ROM emulator to also load GT1 files directly to RAM and, while programs are actually loaded and run, I got lots of hangs and bad behavior, so there is something wrong. This is my loading procedure: - Stop the Gigatron while refreshing the video to be sure the vCPU emulator ...

Hi, Today I received the PCBs for the ROM emulator. idrd1.jpg And I assembled one board... isrd2.jpg isrd3.jpg And after plugging it into the Gigatron, and of course some software tweaking, I was able to load a ROMv3 image from an SD card and to run it isrd4.jpg isrd5.jpg There is still a lot of sof...

Hi, This time I tried a different version with registers at the output: vd2.gif The XOR gates double the clock rate for U2 flipflops. The OR gate may be replaced by 2 diodes and a resistor, but only if chips are 74HCs, not true TTLs like those in the prototype. The Gigatron clock is a square wave. A...

Yes, I know about the 74HCU04. It is well suited for linear amplifiers (as does the 4069U). But when it comes to oscillators the problem with the HC04 or the HCT04 is to oscillate at some other frequency than the crystal (a buffered inverter with a feedback resistor is a ring oscillator already). Th...

Hi, After receiving a Gigatron kit I finished assembling it yesterday late at night. I built a fully socketed one, and this allowed me to do some experimentation regarding its clock oscillator. First, replacing U1 by a 74HC04 I got a near perfect square wave for the clock. With this clock, and witho...