P1

Defines the port used on RS-232 serial communication. Possible values are 1: COM1 (default), 2: COM2, 3: COM3, or 4: COM4

P2

Defines a baud rate, in bps. Possible values must be in the range between 0 (zero) and 65535. The default value is 9600 bps

P3

Not used, leave it in 0 (zero)

P4

Not used, leave it in 0 (zero)