help - z85c30 controller

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We are trying to configure a Z85C30 communications controller for
communicating with both it's channels simultaneously (We are using
Rabbit 3000 as our microprocessor). Channel A is working well as we
have a crystal connected across it. Channel B also has a crystal across
it, but it is not working

Our results so far:
Channel A is working well.
Channel B is showing Transmit Buffer Full and Receive Character not
Available when we try to do I/O on that port.

Are there any issues with usin both channels on the Zilog Z85C30? Any
conflicting settings? We will be very thankful if someone could help.
Any further requests for information for configuration is welcome.

Please help.

Re: help - z85c30 controller

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What do you mean with "Channel B also has a crystal across it" ?
The Z85C30 should have only one crystal for both channels. One can
provide an external clock seperately for each channel, but this is
normally only used for synchronous protocols. I have been using both
channels on the Z85C30 with different processors over many years with
no problems.

  Anton Erasmus

Re: help - z85c30 controller

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...ahh, someone using two of my designs in the same system...

Seriously though, the two SCC channels are identical.  Tx Buffer Full
and no Rx Character Available usually implies that there isn't a clock
for the receiver and transmitter. Make sure that the oscillator on
Channel B is actually oscillating and that you have the clocking
options set up properly.

You might also check the bus timing. Make sure that the channel
select timing is okay, so that you are actually accessing channel B.
But the symptoms say no Tx or Rx clock is present, for some reason.


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