CMOS for NMOS

[Holm Tiffe]

allison via cctalk wrote:

> On 04/15/2018 10:25 AM, David Griffith via cctalk wrote:
> >
> > I'm pondering upgrading the CPU of a Pacccomm Tiny-2 Mk2 radio packet
> > controller from a 6Mhz Z80 processor and SIO to 10Mhz parts.  My
> > problem is that the parts already in it appear to be NMOS.  The family
> > is still being made by Zilog, but for 10Mhz parts, CMOS is all they
> > have.  Can I just drop in CMOS, change out the crystal/oscillator and
> > have things work as expected?
> >
> No, and why?
> 
> Changing to CMOS can cut power drain.  However speeding up clocks can
> make the packet controller
> broken even if it runs!  If you keep the 6mhz clock all will be fine.
> 
> You do not want to alter the output data rate to the modem side.  Also
> the other devices on the bus have
> to be able to run at 10mhz.
> 
> I have in the past upgraded my AmproLB+ to CMOS but that was to lower
> power needs for
> battery operation.  However there was no intent to go faster.
> 
> 
> Allison
> 
> 
> > Here's what are fitted to my TNC.
> >
> > Z84C00BB6
> > Z80BCPU
> > 29125
> >
> > Z8440BB1
> > Z80BSIO-O
> > 29014
> >

Power drain? ..just not interresting here.  Electrically there is no problem
changing an Z80 NMOS Part against an CMOS Version, but you are right in
sight of the speeds of the serial connections.

Z84C00 ..is an CMOS Variant of the CPU, Z8440 is the NMOS Version of the
SIO ..but..
The Z80 Processor needs external memory Parts, RAM and EPROM mostly,
I don't think that the manufacurer of the TNC has fitted faster Parts as
neccessary since they are much more expensive.
Given that, you would not only get an unit that works with wrong speeds
over serial lines, I would expect an just "not working" unit...

Regards,

Holm
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