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Zilog Z8S180 problems - solved

Zilog Z8S180 problems - solved

Some of you may recall that about 3 weeks ago I posted the following:

------------------------------------------------------------------- I seem to be unable to access the new registers on the Zilog Z8S180 CPU, things like the Clock Multiplier register, the additional DMA register etc. When I try to write to these registers my writes seem to be ignored and when I read them back I read FF from most 00 from one. Anyone else having problems with this chip or know the secret code to make it work? :) For all the world it's behaving as if it were a Z180 rather than a S180. I have tried two different chips, one date coded 0106 and the other 0348 - same problem with both.

-------------------------------------------------------------------

The solution: It would appear there are two different mask versions of the Zilog Z8S180 currently in production - Rev K which is purely a static CMOS version of the part and otherwise identical to the Z180 and Rev N which is both a static CMOS part and has the additional features the datasheet for the Z8S180 describes. NB. The only way to tell which part is which is that the Rev K version has "SL1960" printed on the package whereas Rev N does not; although the number is not printed as a prefix or suffix to the part number but on another part of the package in the same manner as a date code.

Nowhere on Zilog's web site is this information available. (Although it might be now!) The latest datasheet for the part (off the website) makes no mention of it. In other words unless one somehow "knows" this, by telepathy perhaps, one doesn't have a bloody clue why the damn chip won't work as the datasheet says it should!

I would have hoped Zilog's tech. support would have immediately known this was a mask problem and alerted me to it - however they didn't appear to have a clue.

Interestingly even "Bill A" of Softools (who kindly responded to my original post) appears to be unawares of this issue and he's been writing tools for these parts for years.

In Zilog's defence I will say that once I alerted senior management to my problem - sparks flew and the issue was resolved in 24 hours.

Mike Harding

Reply to
Mike Harding
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They aren't indentical in that the static parts did add the clock divider and power options in the CCR register.

Rev N also adds problems having to do with the CSIO port which are not in Rev K. My understanding is this is why the SL1960 part was retained. For some users, N's CSIO just didn't work and they had to have the K part. These different revisions are available from Digi-Key by part number: [K]

269-3110-ND = Z8S18020VEC1960 & [N] 269-3109-ND = Z8S18020VEC.

I can't find the errata on the N mask for the CSIO. It was on the site a few years ago.

There is a small hint in the user's manual that the BRG may be special and therefore you might suspect it was added, but yes, it's not obvious. Note that the clock multiplier register doesn't have an official mnemonic either.

I've known of the differences in the masks and of the "SL1960" part for several years. I know of the CSIO problem too in N parts because it has effected customers, which is how they knew to purchase the SL1960's and why Digi-Key carries them. (For a while a customer had one of our "magic" ICE-Cube ICE's which CSIO worked in a system but his stock processors didn't - different parts in each, K in the ICE-Cube, N in stock). It slipped my mind having been working so long with N parts. That's no excuse (and I'm sorry for you I didn't think of it), but this difference should be easily found on Zilog's WEB site, as should errata notices.

Bill A. Softools

Reply to
Bill A.

Big snip

Just to clarify Bill; are you saying this info. _is_ available on the Zilog website or that it _ought_ to be available?

Mike Harding

Reply to
Mike Harding

Hi Mike just wondering - could idea of "upgrading" to ez80 be interesting to you? Andrei Kovalev

why

excuse

be

Reply to
Andrei Kovalev

The Rabbit is the same problem. If they had just maintained compatibility with Z80, let alone 64180/z180, code they could have had a much wider market.

--
Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
     USE worldnet address!
Reply to
CBFalconer

Thanks for the suggestion Andrei but the Z180 is in a mature product with a large code base. I don't think a change to the ez80 would be practical.

Mike Harding

Reply to
Mike Harding

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