i am maziar navahan
i generate simple system expand bus(ssxb!).using standard 8051 UART.
this device good conect to pc and power full software driver run in delphi(the same as other delphi component)and autodetect conected device.
ssxb can work to 255 * 16 device
it using simple rs232 in 375khz(non using any timer of 8051 timer for uart)
you can simple convert to rs485 using simple chip such as 75ls176