Stamp Works -- EXPERIMENT #25: MIXED IO WITH SHIFT REGISTERS

TinkersALot

I am trying to connect a stamp to an output expansion board that has an bit data bus (bidirectional) and 4 control lines. I have that working, but now I'm looking to use less pins from the stamp to make that work.

Referring to the circuit called out in the subject line: Can the outputs side of the 595 be directly connected to the inputs side of the 165 (as in XOUT0 connects to XIN0, etc. ) for form an 8 bit bidectional data bus?

If that can work, then my pin-use-count for this project drops from 12 pins to 8. A worthy goal. If this device combination is not appropriate for that, then is there some other·shift register type of bus transceiver·I should be using instead?

Thanx in advance.
TinkersALot·

Chris Savage

You could connect them in that manner to form a bi-directional bus but you would need one additional consideration to make it work. You would need a R/W line (typical) which, in this case will simply disable the /OE line on the ‘595 for reads. Otherwise the ‘595 will always drive the inputs and you will get collisions with other inputs on the bus. I hope this helps. Take care.

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Chris Savage

Parallax Engineering
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