Panasonic FP Series Programming Manual page 983

System register instructions
Example:
SYS1 'COM1No,D9999' indicates DT9999
SYS1 'COM1No,D0000' indicates DT0
A calculation error occurs if any value except 1–99 is assigned to the DT memory.
4. Header and Terminator (Shared by the COM 1 and COM 2 ports)
Port used
COM1: COM1 port
COM2: COM2 port
Header
STX: STX
NOSTX: no STX
Terminator
ETX: ETX
CR: CR
CRLF: CR + LF
NOTERM: None
982
STX
COM1 ,