Use a SX-28 as a logic master chip

T&E Engineer

What is the best way to approach in design using an SX-28 to replace some logic chips (e.g. 74HC00 NAND, 74HC32 OR and a 74HC138 3/8 Decoder). Would making up a truth table of the possible inputs and outputs and then simplify it through Kanough mapping be the best approach. I want to use an SX-28 to replace a·few chips. Should I use the logic statement or simply use a bunch of IF THEN statements to the·pins on the SX-28 (Inputs and Outputs) as "individual" chips. Hopefully you can follow·what I am saying.

Summary:

Choice A: Through the use of IF THEN statements (e.g. If RA.0 is HIGH AND RA.1 is HIGH THEN RA.2 is LOW, ect..) within an SX-28, create code to emulate per say individual logic chips·and then connect·them together with wires externally to the SX-28 (e.g. SX-28 RA.0 and RA.1 are inputs·to a NAND and RA.2 is the output)

Choice B: Use Karnough mapping to make one master logic statement using various SX-28 I/O pins to emulate this.

I'm thinking that I may have to use Choice B due to the limited amount of pins on the SX-28.

Does anyone know where I can get a good reference to Karnough mapping as I haven't used it in 10 years since college?

Thanks.

Thoughts and Comments?

PJAllen

Karnaugh, sum-of-products

Post Edited (PJ Allen) : 11/6/2006 1:35:47 AM GMT

Sparks-R-Fun

I think that you could use either approach. However, you will want to be mindful of the response delays if you need very fast switching times. Otherwise, if your circuit operates rather slowly compared with the decision making and state changing time of the SX, you should be able to use either option provided you have sufficient memory.

- Sparks