Serial Board using Z80 SIO-2 or Z80-DART

[Tom Szolyga]

ZIlog introduced another serial chip after the SIO chip.  It is the Z80-DART (Dual-channel Asynchronous Receiver)  Basically, it is a SIO die with the Synchronous functions deleted/disabled.  The SIO and DART pinouts are very similar with only four pins different.  (See attached)  I believe a single board could be designed to accommodate either chip by adding 2 jumpers to select between pin functions. Pins 11 can be ignored for connection to a USB-Serial connection.  Pin 27 can be treated as the same function for both parts if the transmitter and receiver clocks are the same.  Only pins 28 and 29 need jumpers to select different functions.  Attached is my schematic for this board.

I welcome comments and would appreciate your feedback.

Best regards,

Tom 

[PianoMatt]

I've been trying to wrap my head around the DART chip and how it relates to the SIO/2. The DART is used in the RS232 expansion for the Amstrad CPC machines, and at some point I want to design and build my own version with the SIO/2 if they're software compatible. Thanks for the info

PianoMatt

[Spencer Owen]

I looked at the DART before I did the SIO/2 board.  I didn't look close enough to the pinout to realise that a dual purpose board would have been so easy - however, the fact that it was discontinued quite some time ago and none of the large distributors had any stock was enough to put me off.  I've just had a quick look and there are a few places claiming to have a few in stock, although whether they exist, are 2nd hand or Chinese knock-offs, I don't know.  Other than that, it looks like a reasonable alternative.  Do you know if the registers are the same too?  (ie will it work with the current SIO/2 ROM?)

Cheers

Spencer

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[PianoMatt]

It looks like they share a common control scheme, based on what I've read here

[Peter Willard]

If they really were based on the same DIE with just some features disabled... it really does make sense that they would be configured and coded the same way... provided you are only after the Async Comms functions

[delph...@gmail.com]

Mouser carries the DART chip in DIP for around $6USD. I thought about using one.

Im sure they are new stock.

https://www.mouser.com/ProductDetail/ZiLOG/Z0847006PSG?qs=GBtv63n%252BAQio6vRFkjrwUg%3D%3D

On Tuesday, October 17, 2017 at 12:17:06 PM UTC-5 Spencer Owen wrote:

I looked at the DART before I did the SIO/2 board.  I didn't look close enough to the pinout to realise that a dual purpose board would have been so easy - however, the fact that it was discontinued quite some time ago and none of the large distributors had any stock was enough to put me off.  I've just had a quick look and there are a few places claiming to have a few in stock, although whether they exist, are 2nd hand or Chinese knock-offs, I don't know.  Other than that, it looks like a reasonable alternative.  Do you know if the registers are the same too?  (ie will it work with the current SIO/2 ROM?)

Cheers

Spencer

On 17 October 2017 at 06:45, Tom Szolyga <tszo...@pacbell.net> wrote:

ZIlog introduced another serial chip after the SIO chip.  It is the Z80-DART (Dual-channel Asynchronous Receiver)  Basically, it is a SIO die with the Synchronous functions deleted/disabled.  The SIO and DART pinouts are very similar with only four pins different.  (See attached)  I believe a single board could be designed to accommodate either chip by adding 2 jumpers to select between pin functions. Pins 11 can be ignored for connection to a USB-Serial connection.  Pin 27 can be treated as the same function for both parts if the transmitter and receiver clocks are the same.  Only pins 28 and 29 need jumpers to select different functions.  Attached is my schematic for this board.

I welcome comments and would appreciate your feedback.

Best regards,

Tom 

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[Clark Martin]

The DART appears to have the same CPU interface as the SIO. THE PART Mouser carries is NMOS, not CMOS.  I haven’t checked the DART specifically but NMOS usually has lower drive capability and lower noise margins.  You might have problems using it on a system with several cards. 

Clark Martin

KK6ISP

Yet another designated driver on the information super highway.

On Nov 23, 2020, at 5:15 PM, delph...@gmail.com <delph...@gmail.com> wrote:



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[Ben Hamilton]

I built a CPS8256 for my amstrad PCW8256 with the DART.  I swapped this out for the Zilog SIO/0 and it also worked without any other changes to code or hardware!  So it looks like they are pin and instruction set compatible - at least for the PCW.  Not sure about the SIO2 but check the data sheet if its compatible with SI0/0.