>On Tue, 11 Nov 1997, Rick Dickinson wrote:
>
>> Fellow PIC-Listers,
>>
>> Based on the feedback I have received, it seems that a design like the
> following
>>  would make the most sense:
>>
>> Port A
>> ------
>>   0 - Serial Data Out   <-- Serial Data Out to the world.
>>   1 - Range Mode Out    <-- Tells the Ranging Unit (RU) what mode to use.
>>   2 - Range Trigger Out <-- Triggers the RU when in one-shot mode.
>>   3 - Data Valid In     <-- Input from RU signals that data is valid.
>>   4 - Serial Data In    <-- Serial Data In from world. Using RA4 allows us
>>                              to use TMR0 rollover to detect start bit.
>
>Using these pin assignments is going to make life difficult for anyone
>who wants to implement a full speed multimaster I^2 C bus interface...
>But maybe few people want that?
>
>John Hallam, AI Dept, Edinburgh University.

Why not reverse port pins 1 & 4 so both serial lines are next to each
other? This would allow those folks who want to give the I2C option a try
to use the same PCB layout, yet still be able to do an AN541-style
bit-banger.

Also, do we really want to lock this into a PIC that must have a bit 4 on
Port A? Especially considering you are giving up the T0CKI line to do so.
Maybe another port would be more appropriate? We could go with nybble-mode
transfers instead of using all of Port B for this purpose (this would be my
preference). Or maybe we should look for a way to get rid of the Range Mode
pin altogether.

Also, what's the feeling about taking the SSU stuff to a private
distribution list & posting periodic updates back to the PIC list?

--BN

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