'Any Ideas to add more Ports ???? -Reply'
ter (Chee Foon Tiang)
On Mon, 20 Jul 1998, Ricardo Ponte G wrote:
> I«m working with the PIC16C715. It has 13 I/O lines but I
> manipulate one LCD, read some extern values and control some
Why not use a *cheap* 74HC4094 for output purposes ?
You need only three of your PIC port and you can cascade
74HC4094s to as many outputs you need (of course beware
of fan-outs... with the PIC you should'nt worry that much! ).
For inputs, you can use the 74HC4051 8-to-1 multiplexor
with the selector pin driven by the expanded 74HC4094.
You only need one input pin.
So, with just 4 port utilized, you can have 8-inputs and as many
outputs you need and can design-in.
And these standard logic ICs is pretty fast and the limitation will
be on the PIC.
You can also save on I/Os if you run your LCD (HD44780 based,
I believe) in 4-bit mode.
Design & Applications Lab
Hitachi Semiconductor(M) Sdn Bhd
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