kb0jjn
New member
I have been working a two Galaxians lately and had one working and one kept barking, still is. The working one I had
put the daughter board in wrong and kill EVERYTHING on it, roms and ttl chip (chip select). I still can't believe that I did this ;but sometimes these little set backs are just what we need to take a giant step forward < Real Genius; Val Kilmer. Some say I look kind of like him...
http://en.wikipedia.org/wiki/Val_Kilmer
So I decide to do a rom hack and try to get the barking dog to stop. Rom hack in and still watch dog barking at the 'birdie' sounding logic probe on reset (pin 26 of z80).
I have tried to let it bark for some time, 3 to 5 seconds then hold high and most things look fine. Address line a3 is stuck high ALL OF THE TIME. It never changes state. I am wondering now is this bcause of the rom hack or is there another issue with the a3 line from cpu (z80a) to the 74ls138's. This is an addressing problem and not one of my better areas...
Is this caused by the single rom hack with 2 games on it (image is GALAX_7F.256) that I programmed on a 256 eprom and put this chip in proper position and wiring. Looking at the paper work I only messed with the a11-a13 addressing pins, CE and OE. a12 from 256 eprom pin 2 goes to chip 7D pin 5. CE get ground and OE to chip 8E pin 13. a11 and a13 to chip 7D pin 3(a11) and pin 7(a13). Nothing there about the a3 line but since I did take some eproms out of the circuitry would a3 stay in a high state?
Now I may just move the rom hack to the otherwise working board but I want to get that back working proper first. I need some new eproms but they getting up ther$. I have several of the 256 eproms and my last order from Riptor has some 24 and 28 pin sockets so.....Thoughts anyone?
put the daughter board in wrong and kill EVERYTHING on it, roms and ttl chip (chip select). I still can't believe that I did this ;but sometimes these little set backs are just what we need to take a giant step forward < Real Genius; Val Kilmer. Some say I look kind of like him...
http://en.wikipedia.org/wiki/Val_Kilmer
So I decide to do a rom hack and try to get the barking dog to stop. Rom hack in and still watch dog barking at the 'birdie' sounding logic probe on reset (pin 26 of z80).
I have tried to let it bark for some time, 3 to 5 seconds then hold high and most things look fine. Address line a3 is stuck high ALL OF THE TIME. It never changes state. I am wondering now is this bcause of the rom hack or is there another issue with the a3 line from cpu (z80a) to the 74ls138's. This is an addressing problem and not one of my better areas...
Is this caused by the single rom hack with 2 games on it (image is GALAX_7F.256) that I programmed on a 256 eprom and put this chip in proper position and wiring. Looking at the paper work I only messed with the a11-a13 addressing pins, CE and OE. a12 from 256 eprom pin 2 goes to chip 7D pin 5. CE get ground and OE to chip 8E pin 13. a11 and a13 to chip 7D pin 3(a11) and pin 7(a13). Nothing there about the a3 line but since I did take some eproms out of the circuitry would a3 stay in a high state?
Now I may just move the rom hack to the otherwise working board but I want to get that back working proper first. I need some new eproms but they getting up ther$. I have several of the 256 eproms and my last order from Riptor has some 24 and 28 pin sockets so.....Thoughts anyone?