Hitachi H252C PROTOCOL STRUCTURE

[Guest bithappy]

:*-( hI, List, I am attempting to create my own scada system with vb 6 interfacing with the Hitachi 252 series plc. I have read a book by Tom Leonik who shows how to do this basically with an AB micrologix. (Rockwell). Allen Bradley use various serial protocols to manage the communications such as dh+ Data Highway etc, my first question to you all is what is the protocol that the Hitachi 200 series uses via the plain old serial port ( no modbus) etc just straight rs 232 or 422, so I can write up some code in vb6 to read and write data to this plc from my serial port. I have a basic programming manual for this plc but it doesnt explain much , it seems programming info for these hitachi's is pretty poorly available. I know I can get of the shelf scada with drivers already included however I wish to teach myself how to program vb6 to do the scada , that way I'll learn how its done ..please advise me on the nitty gritty as I also realise there are opc servers that achieve this too , But i want to learn how to do it with my code , cause thats the only way to learn, from ground up. Thanks so much for any help on this issue , regards BITHAPPY.,