Hi Erik,

Yes, I agree that standard PLC have many functions but do we need all the function in a simple application? I doubt.

PLC is just one of the application of uC or uP.I designed this AT89S8252PLC as my entry level PLC only.

A simple PLC is made of uC and some other components, i.e. The heart of Keyence KV10T using Hitachi H8 MCU with extra memory chips only. Since I had a lot of experiences about PLC programming, therefore I want to make my own PLC using 8052 uC and finally it works.

Upon successful of this AT89S8252PLC it save cost to our company when come to making small scale machine, so worth it.

Assume one small scale machine which required only purely sequence control (no analog, high speed pulse and etc), with Keyence PLC KV10 cost about USD200 with 6 inputs and 4 outputs, but AT89S8252PLC cost only USD75 with 16 inputs and 16 outputs, Of course the AT89S8252PLC will be better.

Regards.
Simon Tew