Friday, March 15, 2024

Halcyon clone v2 - Z80 write line never going low?

I'm trying to get my little test ROM to function properly and even basic stuff is not working.  I tracked it down to the Z80 write line never going low.

(highlighted areas are where write is supposed to low)

Looks like maybe a defective Z80?  I'll try another one and see if I get different results.

Wednesday, March 13, 2024

Halcyon clone v2 repair log

  •  Wrote test ROM, then hooked up logic analyzer to Z80 to see how far it got.  Was surprised to see that RESET' was held low.  Using logic probe, looked at U45 which is a flip flop that controls the reset circuit and saw that VRESET' was low despite WRESET' being high.  Hooked up logic analyzer to U45 and saw that pin 13 (flip flop reset) pulses low shortly after WRESET' goes high, which seems like it shouldn't be happening.
  • Hooked up logic analyzer to U44 and saw that pin 8 (which is supposed to be an output) is mirroring pins 12 (an input that takes in a 4 MHz clock) and 11 (an output that takes the 4Mhz clock to the MC6803P microcontroller).  Pin 8 seems to be completely ignoring its inputs, pins 9 and 10.  The Halcyon uses a 74HC08 chip for U44 instead of a 74LS08 (which I am using for my prototype) so I'm going to try the 74HC08 to see if it makes a difference.
  • Replacing U44 with 74HC08 fixed this problem!

Tuesday, February 13, 2024

v1 of Halcyon clone ready for testing

 It most likely has defects, but it's good enough for me to get some of these fabricated and start testing it.



Monday, January 15, 2024

COP421 reader finished!

 I finished building my COP421 reader and it seems to work perfectly.

I confirmed that the Halcyon COP421 program is identical to the dump that Mark Broadhead made over 20 years ago of the arcade Thayer's Quest COP421 program.

I uploaded everything (source code, CAD files, etc) to github, which you can find here: https://github.com/rulecity/COP421Reader/



Saturday, January 13, 2024

Building a COP421 reader

 

Just to be sure I get every last detail that I can from the Halcyon that I have on loan, I've decided to follow the excellent instructions from here ( http://john.ccac.rwth-aachen.de:8000/patrick/COPSreader.htm ) and create my own COP reader to read Halcyon's COP chip.  Now, I am 90% sure it will be the same one as on Thayer's Quest arcade, but I need to make 100% sure.  I could use the same device as in the link, but I think it will be more fun/challenging to create my own.  I am re-using some parts that I've already used with Dexter since I'm more familiar with them (mainly the FT232 USB IC and the ATMega644p microcontroller at 18.432 MHz).

Thursday, March 23, 2023

Building a Halcyon cartridge reader

 Using the Thayer's Quest arcade schematics and the Thayer's Quest arcade 'cartridge', I made a simple PCB adapter so that the cartridge could be read in an EPROM reader.


First test was the arcade 'cartridge' to make sure I didn't damage anything.


After that worked, I tried the actual Thayer's Quest Halcyon cartridge.



Conclusion?  It works!


Monday, March 6, 2023

Bega's Battle - Sync Generator Replacement - Testing with Super Don NTSC decoder

 

I don't have a Data East chroma PCB so I decided to try rigging up a Super Don NTSC decoder.  The colors are a little off, but it works well enough for testing!