Search found 21 matches

by pythag
28 Apr 2019, 20:06
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

So getting closer and learning more at the same time (which was the original aim of this!) I bit the bullet and wired up the AC register outputs to the Arduino so I could monitor them... this immediately revealed a stuck-at-one bit (AC4)... This was quickly traced to a misplaced wire. The subsequent...
by pythag
28 Apr 2019, 19:06
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

Thanks for the video link - both really interesting and really useful! It's certainly helped me understand more about the branch control logic. Back at the problem in hand - my low PL line on the breadboard is because the CO line from the ALU is low during the BCC instruction.... there are so many p...
by pythag
28 Apr 2019, 16:19
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

Okay, so looking at the schematics a low on PL should cause it to load the PC from the Bus, so PL being low means take the branch.... so why does my simulation show a low in PL yet not jump.... Looks like I've made some other silly mistake in modifying the simulator code.....
by pythag
28 Apr 2019, 16:13
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

I wasn't aware of the branch delay slot, nor the Youtube videos! I'll go and listen / learn....

Your Youtube link was broken - were you referring to the Hack42 Lecture?
by pythag
28 Apr 2019, 16:06
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

I've fixed the somewhat obvious error in my Arduino code (it was in the bit that simulates the ram space in the Arduino). Attached is the updated code just for completeness. The simulation now passes that sticking point in the code, and handily prints out what the various control outputs should be o...
by pythag
28 Apr 2019, 00:24
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

Hi Folks, Is there a written guide / notes to Gigatron assembly language anywhere (perhaps as comments in the compiler source somewhere)? I'm really trying to wrap my head around what the first 20 instructions or so do... 0000 0000 ld $00 ;LEDs |OOOO| 0001 1880 ld $80,out 0002 18c0 ld $c0,out 0003 0...
by pythag
22 Apr 2019, 20:37
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

Okay, I must be tired here.... Just looking over the previous trace and logically (in my head at least) the captured data is correct and the simulation wrong: 0005 00ff ld $ff Sim 6: LD A:0006 ins:0 lines: 0011-0 mod:0 lines: 1110 bus:0 W:0 J:0 AC:01, AC7: 0, LD:0 Cap 6: A:0006 R5(5-2):0,0,1,1 ST,W,...
by pythag
22 Apr 2019, 19:30
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

So, latest Observations: (I'm mostly writing this post to force me to explain what I'm observing properly so I spot what I'm obviously missing - I may not even click 'submit!'): I'm now using the Arduino to generate a delayed CLK2. Below is the combined output of: 1st line - disassembly from ROMv3.a...
by pythag
22 Apr 2019, 12:41
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

So after testing this morning I've ruled out a few causes: * Both the instruction decoder and address mode decoder diode logic is working fine (much to my surprise!) * The issue seems to revolve around the loading of the AC register... My AC7 line is first asserted at instruction 0x07 ("0007 ca...
by pythag
21 Apr 2019, 21:09
Forum: Kit assembly gallery
Topic: Assembling Gigatron the hard way
Replies: 29
Views: 22069

Re: Assembling Gigatron the hard way

So having spend most of this evening making my own Arduino based tester I discover this in the repository:

https://github.com/xopr/gigatron-tester ... tester.ino

Still, this will be very useful as it's far more featured than mine....