Epson CW3S16 Operation Manual page 215

Figure E-20. The Printer Adapter Test
Serial Communication Adapter Test
This test requires a special RS-232 Turn-Around Connector
plugged into the port. It must be jumpered as follows:
TXD & RXD (2 & 3) shorted
l
RTS & CTS (4 & 5) shorted
l
DSR & DTR (6 & 20) shorted
l
This test is programmed to read the following data: 9600 baud
rate, odd parity, 2 stop-bits, and 8-bit data. This test first
performs a reset function to check for all possible errors. Then,
the test performs a send function, followed by a receive
function.
E-52 Advanced ROM Diagnostics