Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 05, 2018 3:52 pm
Great news! Can't wait to see output from your temporary dipswitch.
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My first wire wrap: Wilf's AT keyboard interface
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Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 05, 2018 4:09 pm
Before I went to bed I found one switch was not pulled to ground. Maybe it's a resistor or socket that's faulty. Maybe I have time tonight for further investigation with my logic probe.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 05, 2018 10:52 pm
I’ve fixed error on pin 23. It’s now LOW as the others.
The error on pin 5, I don’t know what’s wrong. My only suggestion would be to replace the EEPROM with a new one and see if that fixes the problem.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Feb 11, 2018 10:05 pm
I've changed the EEPROM, and checked that A13 is not connected to anything other than A5 on the EEPROM. It didn't fix anything.
Can anyone suggest why A13 is Pulse-Low, when everything else is Pulse-High-Low?
When the card is not connected to the ZX81, then A13 is Pulse-High-Low.
Can anyone suggest why A13 is Pulse-Low, when everything else is Pulse-High-Low?
When the card is not connected to the ZX81, then A13 is Pulse-High-Low.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Sun Feb 11, 2018 10:28 pm
I just realized my EEPROM never gets Chip Enable signal, at the Arduino controller is not yet implemented. I need a switch for Chip Enable instead.
Back to the drawing board.
Back to the drawing board.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 12, 2018 12:12 am
Why is Vss on EPROM connected to 0V? Is that supply or sink voltage?
Nevermind it's ground.
Nevermind it's ground.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 12, 2018 12:18 am
I assume it’s GND on the 28C64 EEPROM I’m using. Look at previous post for my schematic
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 12, 2018 12:30 am
Is it significant A13 is not connected to ROM? Nor internal RAM?
A14 and 15 connect to ULA.
A14 and 15 connect to ULA.
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 12, 2018 12:34 am
I saw the post and schematic but I second guess everyone and every thing as there are land mines everywhere!
Re: My first wire wrap: Wilf's AT keyboard interface
Posted: Mon Feb 12, 2018 12:36 am
The ROM routine sets RAMTOP for 1k ( I assume you do not have a memory pack on back) and maybe never addresses with A13.