Search found 5 matches

by Martin_H
06 Apr 2019, 21:40
Forum: Kit assembly gallery
Topic: Clock circuit check
Replies: 3
Views: 476

Re: Clock circuit check

As a sanity check, measure the voltage at the power input jack. If that's good, then look at the polarity of the Zener diode D1. The zener is installed across the power rails in the opposite direction of a normal diode. If installed the wrong way it would become a short and would definitely drop the...
by Martin_H
02 Apr 2019, 22:01
Forum: Hardware and software hacking
Topic: Another Gigatron Instruction Set Question.
Replies: 2
Views: 462

Re: Another Gigatron Instruction Set Question.

Thanks for the reply and the documentation pointers. The ROM code makes much more sense once you know that store can writes to ram and a register in a single instruction.
by Martin_H
01 Apr 2019, 22:51
Forum: Hardware and software hacking
Topic: Another Gigatron Instruction Set Question.
Replies: 2
Views: 462

Another Gigatron Instruction Set Question.

Some aspects of the Gigatron remind me of the 6502, which shouldn't be a shock since they're both eight bit CPU's with three registers. One similarity is that it is possible to load X or Y with a load instruction, or to move a value from the accumulator into them. For example, I think this: ld [$17]...
by Martin_H
30 Mar 2019, 00:19
Forum: Hardware and software hacking
Topic: Decoding Branch Instructions
Replies: 2
Views: 335

Re: Decoding Branch Instructions

Thanks for the reply. Glad that it's the web page and not me.

Also thanks for the link to the control unit. Reading through the schematics is next on my agenda.
by Martin_H
29 Mar 2019, 21:34
Forum: Hardware and software hacking
Topic: Decoding Branch Instructions
Replies: 2
Views: 335

Decoding Branch Instructions

First off. Nice Job on the Gigatron! I've been reading through the documentation, and I watched your YouTube video on how it worked. It was quite interesting to see how you did without microcode for instruction sequencing. To really understand it, I read the ROM assembler, and mapped the machine cod...