Search found 32 matches

by gesari
19 Apr 2019, 13:40
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 38
Views: 38329

Re: High resolution mode?

Could you check if the resistor does the trick? I got no equipment here to test it, and simulation is not always like reality...
by gesari
19 Apr 2019, 10:23
Forum: Hardware and software hacking
Topic: In Circuit EPROM emulator and debugger
Replies: 20
Views: 13986

Re: In Circuit EPROM emulator and debugger

A first schematic is attached.
by gesari
19 Apr 2019, 09:27
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 38
Views: 38329

Re: High resolution mode?

I think the easiest way to get an 50% duty clock is to connect a 1k2 resistor in parallel with C2. This will also lower the oscillation amplitude at the inverter input (pin 1) avoiding negative voltages. And I see no problem with slow RAMs. Even the 70ns part has a write pulse width of 50ns, less th...
by gesari
17 Apr 2019, 13:25
Forum: Hardware and software hacking
Topic: In Circuit EPROM emulator and debugger
Replies: 20
Views: 13986

In Circuit EPROM emulator and debugger

I'm planing to use the Gigatron as a teaching tool for computer science because I think it fills very well the link between simple digital circuits, like decoders or counters, and microprocessors. The main problem for this is the EPROM. Its erasing time is too long and you have to remove it every ti...
by gesari
15 Apr 2019, 13:25
Forum: Hardware and software hacking
Topic: Good Clock Waveform
Replies: 2
Views: 3957

Re: Good Clock Waveform

It doesn't look much square.
If U1 is replaced from a 74HCT04 to a 74HC04 I think you can get a better square wave.
by gesari
15 Apr 2019, 10:25
Forum: Hardware and software hacking
Topic: Diodes
Replies: 3
Views: 3421

Re: Diodes

So they are Schottky barrier diodes. This makes more sense, because new germanium diodes are difficult to find (not in Digikey, nor Mouser...) Just for comment: You can save one diode in the AND gate. Just remove one diode and place the resistor in ts place instead. This two component AND gate will ...
by gesari
15 Apr 2019, 10:11
Forum: Hardware and software hacking
Topic: Some ideas for an enhanced Gigatron
Replies: 5
Views: 4414

Re: Some ideas for an enhanced Gigatron

Excuse my poor english. The images were in random order, not scrambled... And the 4053 CMOS 'intruder' was just a sort of joke. In fact all chips are CMOS. This chip would end up being a 74HC4053, with a '74' in its name :) And yes, I understand simplicity here is the main goal. The upgraded carry o...
by gesari
14 Apr 2019, 14:18
Forum: Hardware and software hacking
Topic: Some ideas for an enhanced Gigatron
Replies: 5
Views: 4414

Re: Some ideas for an enhanced Gigatron

And also the SPI schematic is incomplete. It should be this:
SPI.gif
SPI.gif (26.74 KiB) Viewed 4413 times
by gesari
14 Apr 2019, 14:16
Forum: Hardware and software hacking
Topic: Some ideas for an enhanced Gigatron
Replies: 5
Views: 4414

Re: Some ideas for an enhanced Gigatron

As I feared all the images were scrambled... Sorry about that.
by gesari
14 Apr 2019, 14:12
Forum: Hardware and software hacking
Topic: Some ideas for an enhanced Gigatron
Replies: 5
Views: 4414

Some ideas for an enhanced Gigatron

Long post... Hi, Here I'm presenting some ideas about how to improve the Gigatron. I know there is work being done about this, mainly about I/O (SPI, namely), and I think these changes deserve some discussion before ending with dozens of different Gigatrons. In particular I found the Gigatron is lac...