this PLC based on 8051
i designed totally myself

it is programmed in STL
(STL = Statement List )
a language with 60 instructions

You write the program in the editor
of the utility program
(which u can download from my webpage
just click on the picture of the utility program)

and then transfer it to PLC via serial port

you can monitor running program
and watch inputs and outputs and variables
on the PC screen during the PLC running

my webpage again
http://abone.superonline.com/~plc/

for english version of the webpage go to
http://www22.brinkster.com/anotherbrick/indexe.htm