Bill,
90+% of all POS displays use the Epson ESC/POS command set... 9600baud,no parity, 1 stop bit and the following command set:

ctrlH: back one position (non-destructive)
ctrlI: forward one position (non-destructive)
ctrlJ: line down
ctrlK: home
ctrlL: clear screen
ctrlM: beginning of line
ctrlX: clear line, return to beginning
ctrl?ctrlJ: line up

This PDF shows coding for other common command protocols.

Hope that helps...