port expander 450 outputs

[nandhu015]

Need to 450 outputs to be controlled by PIC or ATMEL controller.

Multiplexing not possible.

Advise low cost solution for port expander.

 

[betwixt]

Parallel addressing will need 9 address lines, 1 data line, a latch signal and at least 30 discrete ICs (28 x 16 bit ports plus some glue logic).
Serial addressing would need 1 address line, 1 data line, a latch signal and shift registers

You might consider that PIC's make good shift registers themselves and have higher pin current capability than standard CMOS devices. Alternatively, the extra 'intelligence' they offer over simple shift registers means you might be able to develop a simple protocol to control outputs without daisy chaining them and it would be expandable too. For example you might use a master UART to address lots of PIC in parallel and send "449,1" to turn output 449 on and "449,0" to turn it off.

Brian.

 

[nandhu015]

@betwixt
Thanks for the response

Can you point out some low cost, high pin count controllers (any brand) that will suit my need..

 

[betwixt]

What response speed do you need?
To use SPI or serial you only need a few pins, any remaining can be used as expander ports. The software is very simple and very little memory is needed.
Look at: https://www.microchip.com/maps/microcontroller.aspx
and see if you can find a high I/O pin count device that suits your needs.

Brian.