[sdiy] Ursa major UART: WD2123

[Rutger Vlek]

Thanks for all the replies! 

The use of the WD2123 in the Ursa Major is fairly strange, as it is intended for connection of an (optional) external remote through an RS232 driver and connector. However, the Ursa Major won't start it's CPU properly if the communication with the UART can't be established. Kind of strange to be so dependent on something that's largely intended for "an option". I followed all suggestions in the service manual for debugging the CPU step by step and I have reached the step that says: "swap the WD2123 out for a known working one". Also, from common sense I don't see how CPU startup could otherwise be halted. Even a faulty RS232 driver should not break communication between the CPU and the UART, but merely lead to bogus input data from a non-existant remote controller.

So my hopes are that a new WD2123 will get the CPU fully started again, as I'm out of alternatives.

Rutger


On 26 okt 2016, at 17:30, MTG wrote:

> That's a tough one. The "DEUCE", Dual Enhanced Universal Communication Element. Does it require a baud rate generator chip? I assume you've ruled out the obvious -- the chip(s) between it and the world?
> 
> Long shot, but here is one maybe:
> http://www.cedar--rapids.com/Industrial-Equipment-/Oakhill-Jackson-/Welding-Cutting-/Lsi-WD2123-pl-wd-40-pin-vintage-controller.PHP
> 
> 
> On 10/26/2016 2:11 AM, Rutger Vlek wrote:
>> Hi guys,
>> 
>> I'm looking for a fine example of unobtainium: a WD2123 (western digital) double UART IC. It was used in a Ursa Major 8x32 that I'm working on, and it needs a new one to get the CPU running again (the UART blocks it). They used to use these chips in various vintage computers too (FDD3000, etc). Anyone have a working one?
>> 
>> Regards,
>> 
>> Rutger
>> 
>> 
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>> 
>> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy