Subject:
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(no subject)
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Fri, 9 Aug 1996 05:34:31 GMT
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Original-From:
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Brian Lavery <[blavery@]AntiSpam[acslink.aone.net.au]>
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Viewed:
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1567 times
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More MUSINGS follow.
Seeing as my job gets progressively more MANAGEMENT than TECHNICAL
these days - is it really inevitable over the years?? - this
software/electronic/mechanical exercise called robotics seems a
good hobby to do all those things that used to be a paid job,
but must have been fun anyway!
********************************************************
* MUSINGS ON THE SUBJECT OF HANDYBOARD INTERFACING *
********************************************************
* Plain digital I/O (from the data bus) *
********************************************************
The conventional method of digital I/O
======================================
|-----|
Y23 ->|Wr |
| | (I use the "[]" symbol to mean LATCHED)
D7 ->| []-->
D6 ->| []--> 8 latched outputs
D5 ->| []-->
D4 ->| []-->
D3 ->| []-->
D2 ->| []--> Consumes a Chip Select for each 373.
D1 ->| []--> Needs 8 data bits onto the CPU bus.
D0 ->|373 []--> Writes all 8 bits together.
|-----|
|-----|
Y33 ->|Rd |
| |
D7 <-| |<-- 8 digital inputs - all read together
D6 <-| |<--
D5 <-| |<--
D4 <-| |<--
D3 <-| |<--
D2 <-| |<--
D1 <-| |<--
D0 <-| 244 |<--
|-----|
Simple but better digital I/O:
==============================
|-----|
Y23 ->|Wr []-->
| []--> 8 latched outputs - but only 1 bit on data bus
D0 ->| []-->
| []-->
A2 ->| []--> Can re-use the same Chip Select (Eg Y23)
A1 ->| []--> for each of the data bits D0 - D7,
A0 ->| []--> giving up to 64 outputs per CS.
|259 []-->
|-----| Separate WRITE operation per bit of I/O,
which suits robotic applications well.
|-----|
Y33 ->|Rd |<-- 8 digital inputs
| |<--
D0 <-| |<--
| |<-- Again, can expand to 64 inputs for the cost
A2 ->| |<-- of only one CS decode.
A1 ->| |<--
A0 ->| |<--
| 251 |<-- 251 & 259 are a little
|-----| hard to come by. Some
places dont seem to
bother stocking them.
====================================================================
& I think I was wrong a couple of days ago re OC5 output being
reconfigurable as IC4. The 68HC11E CPU has that, but the 68HC11A does
not seem to.
Cheers to all!
Brian Lavery
Syndey Australia.
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