Z80 Homebrew and EPM 7032 CPLD - Page 1
Forum section: electronics / general

author: FlyMario
author_rank: Contributor
timestamp: March 05, 2019, 02:15:43 pm
content: So I have been building a Z80 computer and on Rev 3 so far. About to greate Rev 4 and make it more modular like the RC2014.I have a lot of these EPM7032 CPLDs from Altera. The pins are 5-volt tolerant yet the CPLD has a 3.3v core. I wonder if it isn't wise to use Logic Level converters on the pins coming from the Z80 or other 5v hardware.It makes me a bit concerned that I don't find examples of these chips being used with Z80 yet it would be great to handle GLUE logic.Any of you have suggestions or observations you could share with me?Thanks!

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 05, 2019, 02:20:56 pm
content: I just bought rather a lot of these chips with the hope of using them for custom chip replacements in old arcade games.The only trick I believe is you have to pull up the outputs to 5V to avoid the multi-logic feature outputing 3V3.I wish us both good luck

author: obiwanjacobi
author_rank: Super Contributor
timestamp: March 05, 2019, 02:45:38 pm
content: I use the Altera Max II and found a document that describes how to use it with 5V (Chapter 8 ):https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/max2/max2_mii5v1.pdfI have implemented it and seems to work fine.https://github.com/obiwanjacobi/Zalt/tree/master/Decoder%20Board%20v1.0%20-%20lockedPerhaps there is a similar document for the EPM7032?Otherwise sacrifice one for a test or two?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 05, 2019, 03:16:32 pm
content: I'm planning to use S series Max 7000....https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ds/archives/m7000.pdfQuote

author: FlyMario
author_rank: Contributor
timestamp: March 05, 2019, 03:39:03 pm
content: That is interesting because I use the EPM7032AEL 44 Pin and the EPM7032AETC 44 pin neither of which show a limitation from the datasheet to handling 5v logic.Now to be honest I have had an EPM7032 for weeks now having an Arduino pulsing it with 5v. Not convinced this means anythingIt seems I have conflicting datasheets maybe. I am confused now. below is the datasheet I have been working from.https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ds/m7000a.pdfAm I misinterpreting something that you guys notice? I do have logic level shifters so I am not going to be that upset. Wanted to avoid that extra circuitry lol.Thanks,FlyMario

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 05, 2019, 03:54:44 pm
content: Inputs are fine, it's the outputs and driving old crusty TTL chips that is the only issue... and that requires the pull-ups to get safely within the family logic levels.

author: tsman
author_rank: Frequent Contributor
timestamp: March 05, 2019, 03:55:26 pm
content: Quote from: FlyMario on March 05, 2019, 03:39:03 pmDifferent part. You've got a MAX7000A which has MultiVolt for all packages but NivagSwerdna has a MAX7000 which has MultiVolt for all except the 44 pin parts.

author: trevatxtal
author_rank: Contributor
timestamp: March 05, 2019, 04:53:42 pm
content: If memory serves me right the Z80 has Tri state Data and Address lines.But you may be aware of this. On the boards my company designed we used Tri state buffers, I possibly a 74241 or 74240. ls ver available.Hope this helps.Trevor

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 05, 2019, 05:04:21 pm
content: Good point. I am using EPM7128SLC84-15; hope I didn't confuse.

author: nick_d
author_rank: Regular Contributor
timestamp: March 07, 2019, 10:28:50 am
content: The CMOS Z80s have 74HCT style inputs with a threshold around 1.2V, this was originally for NMOS compatibility but also means no special action is needed for 3.3V logic compatibility (since your 3.3V device is 5V tolerant).cheers, Nick