Very interesting. It also makes clear that for OKI at least the -2 is the high speed version compared to the -5 version.
I just looked through the Toshiba datasheet and found no similar warnings. Rich Leary On Saturday, January 17, 2015 at 12:50:48 PM UTC-7, David Fry wrote: > Guys, > > Something has just made me search online and pull the datasheet for the > 82C55, > John mentioned that he uses on all 3 boards the OKI82C55A-2 or the > NEC82C55AC-2 > I use a Mitsubishi M5MB82C55AP-5, so what's the difference between the -2 > and the -5 versions, maybe a little more > than you think, check out page 20,21 and 22 of the OKI datasheet attached > regarding port 'B' instability. > > > Is this a problem for all manufacturers of -5 versions ? Who knows... > > Just another thing to check out > > regards > > David Fry > > > On Saturday, January 17, 2015 at 7:00:19 PM UTC, monahanz wrote: > >> Rich I just pulled my 3 working cards. They have been there for now >> years! >> >> >> >> I have a Signetics 7403A in one, one labeled S7403N, and the third is a >> Ti 74LS03. The first two chips are from 1973, cannot figure out the date of >> the Ti chip. . Interestingly RR1 in the first two cases is a 1K resistor >> SIL, the Ti74LS03 chip has a 680 SIL. >> >> >> >> Two of the 8255s are OKI82C55A-2 the other is a NEC82C55AC-2. I >> generally use Kingston 4GB CF cards (white flower picture on it) but also >> use Maxell 4GB and Patriot 4GB cards are also 100% reliable. >> >> >> >> One board is in a 10 slot motherboard, one a Compupro 18 slot motherboard >> , the other (my main system) is in a 21 slot motherboard. The 10 & 21 slot >> buses have active termination. The “normal” CPU is our Z80 V2 board running >> at 10MHz (1 RAM wait state, 2 IO wait states, 1 ROM wait state). However >> no problems with any of the 8086 family of CPU’s. David was testing the >> 68K and had some issue I seem to remember above 6MHz but I think that was >> the 68K CPU boards “fault”. >> >> >> >> Not sure this helps. But you might want to search around for an old >> 7403. >> >> >> >> At one time I was thinking of doing another version of the board perhaps >> using a SD card as well, but frankly this one seemed to work so well it >> fell to the bottom of the priority list. >> >> >> >> John >> >> >> >> >> >> >> >> *From:* Rich Leary [mailto:[email protected]] >> *Sent:* Saturday, January 17, 2015 8:41 AM >> *To:* [email protected] >> *Cc:* [email protected] >> *Subject:* Re: [N8VEM-S100:6035] Dual IDE/CF V2a >> >> >> >> John, >> >> >> >> It is the most recent release. Silkscreen says 02a. >> >> >> >> Rich >> >> On Friday, January 16, 2015 at 11:43:00 PM UTC-7, monahanz wrote: >> >> Rich are you referring to the V1 or later V3 Dual IDE/CF board. On the >> web page >> >> >> http://s100computers.com/My%20System%20Pages/IDE%20Board/My%20IDE%20Card.htm >> >> >> >> I used Open Collectors 7403’s with 680 Ohm pull-ups for the Read, Write >> and Reset signals on the V3 board. Seems to work fine for me. Been using >> them, (2 boards), for 2 years now. >> >> John >> >> >> >> >> >> *From:* [email protected] [mailto:[email protected]] *On >> Behalf Of *Rich Leary >> *Sent:* Friday, January 16, 2015 9:15 PM >> *To:* [email protected] >> *Cc:* [email protected] >> *Subject:* Re: [N8VEM-S100:6035] Dual IDE/CF V2a >> >> >> >> John, >> >> >> >> It is puzzling. I am using all 74LS except the two 74S03s and have tried >> both NMOS and CMOS varieties of the 8255. >> >> >> >> I have gone back to the CF and IDE specs and looked hard at the signal >> level specifications. My preliminary look seems to conflict with the build >> notes. >> >> >> >> The CF spec defines three type of signals at the interface and one of >> them (Type 1) does specify a 4V Vih for some signals. Other signals use >> either 2.0V or 2.8V. >> >> >> >> What is confusing is that the Type 1 signals are the address lines (An) >> and the data lines (Dn). The IORD, IOWR, and CSn (chip select n) lines are >> all Type 3 and the card inputs for those lines only require Vih of 2.8V to >> trigger the Schmitt Trigger that Type 3 uses. But the IORD, IOWR, and >> CSn lines are what are driven by the 74S03 or 74H03 ICs on the S100 board. >> RESET is a Type 2 signal and Vih need only be 2.0V. >> >> >> >> The only on-board pull ups are those associated with the 74S03 or 74H03 >> ICs and they are very low value. The schematic shows 680 ohm but the notes >> suggest something like 330. >> >> >> >> What is also important to note is that the CF card input leakage current >> is very low at +- 1 uA so whatever is driving all CF lines is doing so at a >> very low load level. Since the IDE An and IDE Dn lines all connected to the >> 8255 ports that probably explains why those lines may be OK. In my Toshiba >> TMP82C55A datasheet it shows a Voh of Vcc-0.8V for Ioh of -100uA. As long >> as the load seen by the 8255 is just one of two CF cards with a total >> leakage of +- 2 uA that would work. But any 8255 outputs driving TTL inputs >> may have a low or marginal Voh at least for Dn and An. >> >> >> >> I can see no reasons for use of the high power - high speed gates and the >> low value pull ups on the IORD, IOWR, CSn, and RESET lines. As I read the >> specs it looks like those gates can be 74LS00's with no pull up or much >> higher pull ups (50K ?). In addition if we do not need to switch the higher >> currents associated with the low value pull ups that will reduce noise >> levels on the board. >> >> >> >> I need to read the CF spec again and do a line by line gozinta versus >> gozouta analysis before reaching for the de-soldering braid and solder >> sucker. It is possible that I have completely misread the spec and if so I >> apologize for the confusion but right now I think there may be some >> low-hanging fruit that should be harvested. Even if what my initial look >> indicates proves correct there may be other issues. >> >> >> >> I will get back to everyone hopefully by late on the 18th. >> >> >> >> If anyone has reason to show me the error in my thinking please fire away >> - at my age my skin has absorbed many blasts and a little more will not >> hurt. >> >> >> >> Rich Leary >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "N8VEM-S100" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. >> >> -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
