Post by thread:Any Ideas to add more Ports ???? -Reply

On Mon, 20 Jul 1998, Ricardo Ponte G wrote: > I«m working with the PIC16C715. It has 13 I/O lines but I got to > manipulate one LCD, read some extern values and control some devices. > 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. Regards, Peter Tiang Design & Applications Lab Hitachi Semiconductor(M) Sdn Bhd