Yes, that is good. On Jul 5, 2016 10:31 PM, "Mike Stein" <[email protected]> wrote:
> Continuity M5-12 to M6-20? > > ----- Original Message ----- > *From:* Josh Malone <[email protected]> > *To:* Model 100 Discussion <[email protected]> > *Sent:* Tuesday, July 05, 2016 10:13 PM > *Subject:* Re: [M100] 32k M102 suddenly showing 24k > > No, I'm guessing that the chip is holding its enable line high and never > activating. I haven't read very far into the chip - I should finish the > test. I'm just concerned that the enable line never goes low on this chip. > > On Jul 5, 2016 10:10 PM, "Stephen Adolph" <[email protected]> wrote: > >> Are you saying there are only 3 bad cells? >> >> Could just be a bad trace. >> The data and address bus are muxed. >> >> I would buzz out every pin on the suspect ram for zero ohms, to the 'end" >> of the bus. You may just find a weak signal, >> >> >> >> On Tuesday, July 5, 2016, Josh Malone <[email protected]> wrote: >> > Thanks - just what I needed. So, I wrote a quick sequential RAM read in >> BASIC and I can't see any activity on the *CE line on M6. Writing a quick >> destructive RAM test, when writing to 32768 to 32790, the value I read back >> is just the offset from 32768 (i.e., 32768 = 1, 32769 = 2). I'm assuming >> that I'm actually reading the data line part of the shared address bus >> that's been latched in but never released. >> > >> > Soooo... does this sound like the SRAM or the decoder circuit? I'm >> leaning toward the SRAM, personally. All the other chips are working fine. >> I've also verified connection from M5 pin 12 to the *CE on M6. I'd have to >> disconnect the decoder from the SRAM to really see who's at fault, and if >> I'm getting out my iron to work on M5 (the decoder) I may well replace the >> darned thing since it's SMT. >> > >> > Guesses? >> > >> > Thanks again for everybody's help. >> > >> > -Josh >> > >> > On Tue, Jul 5, 2016 at 11:00 AM, Mike Stein <[email protected]> >> wrote: >> >> >> >> pp. 7 & 8 of the Tech Ref: >> >> >> >> ftp://ftp.whtech.com/club100/doc/m102TechReference.pdf >> >> >> >> ----- Original Message ----- >> >> From: Josh Malone >> >> To: Model 100 Discussion >> >> Sent: Tuesday, July 05, 2016 6:30 AM >> >> Subject: Re: [M100] 32k M102 suddenly showing 24k >> >> >> >> Once I figure out the memory map that was exactly what I was going to >> do while probing the chip. >> >> >> >> On Jul 4, 2016 10:56 PM, "Doug Jackson" <[email protected]> wrote: >> >>> >> >>> You could poke directly at the relevant memory ranges and see if a >> corresponding peek shows the data >> >>> >> >>> >> >>> On 5 July 2016 12:31:59 pm AEST, Josh Malone <[email protected]> >> wrote: >> >>>> >> >>>> Okay. Thanks for the hints. Anybody know any good RAM diagnostic >> techniques for a 102? It's been a long time since I've used a scope in >> anger on anything but serial or audio. I'll dig into the datasheets >> tomorrow and see if I can gather any clues. A quick probing shows lots of >> address line activity on all four chips - mostly just testing that my scope >> can see these signals... It's been a while. >> >>>> >> >>>> Thanks again, >> >>>> -Josh >> >>> >> >>> -- >> >>> Sent from my Android device with K-9 Mail. Please excuse my brevity. >> > > >
