Very interesting Georg, Can you take some photos of thr PCB sometime if you happen to have your machine open? It is a bit of a pain to reassemble I know.
How did you determine that a 27C64 worked in M13 socket? Besides the obvious that it does work. Because the schematic does not seem to indicate that. Maybe your board is very different. Thx Steve On Monday, November 14, 2022, Georg Käter < [email protected]> wrote: > Hello together, > > > > my Tandy 200 (European version, build in 1985) uses main PCB #-PLX178AHIX. > This board accepts > > standard UV-eraseable EPROM 27C256 (32kB) and 27C64 (8kB) 150ns type w/o > any modification. > > Maybe there are other revisions of PCB with different EPROM pinout I´m > not aware of. > > > Regards > > Georg > > Georg Käter > Gangolfsweg 44 > <https://www.google.com/maps/search/Gangolfsweg+44+%0D%0AD-52076+Aachen?entry=gmail&source=g> > D-52076 Aachen > Tel. : +49 2408 7194987 > Fax. : +49 2408 7196758 > Mobil : +49 171 4839954 > E-Mail : > [email protected] > > ========== Ihre Nachricht ========================================== > > *von* : Brian K. White <[email protected]> > *gesendet* : Montag, 14. November 2022, 16:24 > *an* : [email protected] > *Betreff* : [M100] custom key mapping generator for Tandy 200 > > __________ Originalnachricht _______________________________________ > > On 11/14/22 10:11, Brian K. White wrote: > > On 11/14/22 09:12, Brian White wrote: > > The datasheet says to rest vpp at vcc. Most do, even if elsewhere they >> > also say that writing is disabled as long as vpp is below vpp and the >> > only low limit is pretty much the same as for any other pin, like 0.5 >> or > 0.7 below vcc. > > derp I mean the low limit is a little below GND or VSS not VCC. > > Although a Microchip 27C64 datasheet I happen to be looking at at the > > moment does actually say the vpp read voltage is min vcc-0.7, max vcc. > > > More derp, I obviously confused VPP with /WE there. > But pin 27, being /WE (/PGM), still needs to be held at VCC not GND, > although theoretically any writes should still fail without VPP, but still, > you just hold /WE at VCC for reads. > > > > > __________ Ende Originalnachricht __________________________________ > > > *Vertraulichkeitsinformation: *Diese Nachricht ist vertraulich. Die > Informationen dieser Nachricht sind ausschließlich für die persönliche > und vertrauliche Verwendung durch den/die oben genannten Empfänger > bestimmt. Wenn Sie kein beabsichtigter > Empfänger sind, bitte lesen, kopieren und verwenden Sie die Nachricht > nicht. Machen Sie sie nicht anderen > zugänglich. Bitte informieren Sie uns umgehend über den Zustellfehler und > senden Sie die Originalnachricht > per E-Mail an uns zurück. > > > *Confidentiality Notice: *This message is confidential. The information > contained in this message is intended only for the personal > and confidential use of the recipient(s) named above. If you are not the > intended recipient, please do not > read, copy, or use it and do not disclose it to others. Please inform us > immediately of the delivery error > and return the original message to us via e-mail. >
