1)What should i do to send 234 as 8 bit data?

Use the Chr function. I.e. MSComm1.Output=Chr(234)

2)The data sent or received by UC is in HEX format. Keeping this in mind, which of the InputMode property(comInputModeText or comInputModeBinary)should be chosen ?

comInputModeBinary

3)If UC sends data 234 as 8 bit data, what will be the output of instruction:
Text1.Text =MSComm1.Input ? (ASCII character of '234' or '234')

It will be the ASCII character 234

Regards,
Rob.