Search found 31 matches

by gesari
04 Jun 2019, 17:51
Forum: Hardware and software hacking
Topic: In Circuit EPROM emulator and debugger
Replies: 8
Views: 352

Re: In Circuit EPROM emulator and debugger

A few terminal captures, using 'minicom -c on'
isrd1.gif
isrd1.gif (76.4 KiB) Viewed 60 times
isrd2.gif
isrd2.gif (81.13 KiB) Viewed 60 times
isrd3.gif
isrd3.gif (80.82 KiB) Viewed 60 times
isrd4.gif
isrd4.gif (80.27 KiB) Viewed 60 times
by gesari
04 Jun 2019, 10:27
Forum: Hardware and software hacking
Topic: In Circuit EPROM emulator and debugger
Replies: 8
Views: 352

Re: In Circuit EPROM emulator and debugger

Hi,
A first working version of the ROM emulator firmware is attached here.
ISRDfirmware.zip
(37.58 KiB) Downloaded 3 times
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.
Regards
by gesari
24 May 2019, 07:40
Forum: Hardware and software hacking
Topic: In Circuit EPROM emulator and debugger
Replies: 8
Views: 352

Re: In Circuit EPROM emulator and debugger

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...
by gesari
22 May 2019, 20:40
Forum: Hardware and software hacking
Topic: Loaging GT1 programs to RAM
Replies: 2
Views: 124

Re: Loaging GT1 programs to RAM

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.
by gesari
22 May 2019, 08:02
Forum: Hardware and software hacking
Topic: Loaging GT1 programs to RAM
Replies: 2
Views: 124

Loaging GT1 programs to RAM

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 ...
by gesari
14 May 2019, 20:56
Forum: Hardware and software hacking
Topic: In Circuit EPROM emulator and debugger
Replies: 8
Views: 352

Re: In Circuit EPROM emulator and debugger

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...
by gesari
11 May 2019, 10:35
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 28
Views: 1719

Re: High resolution mode?

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...
by gesari
10 May 2019, 21:43
Forum: Hardware and software hacking
Topic: Oscillator with 50% duty
Replies: 3
Views: 131

Re: Oscillator with 50% duty

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...
by gesari
08 May 2019, 08:08
Forum: Hardware and software hacking
Topic: Oscillator with 50% duty
Replies: 3
Views: 131

Oscillator with 50% duty

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...
by gesari
05 May 2019, 21:01
Forum: Hardware and software hacking
Topic: New form factor Gigatron.
Replies: 3
Views: 276

Re: New form factor Gigatron.

I don't think a better layout will change the max clock frequency too much. Even if the data bus traces are 200mm shorter this length equals only to about 1.3ns propagation delay (wave velocity in tracks is more or less 1/2 the speed of light in vacuum). For a 15MHz clock this delay is only a 2% of ...