Furuno CSH-8L - Manual (Page 81)

8. MAINTENANCE, TROUBLESHOOTING
8-11
SIO test
This test checks the input/output ports (CN-A1, NMEA1/CIF1, NMEA2/CIF2) of
the processor unit. The result for the CN-A1 port is shown as OK or NG (No
Good).
The test for the NMEA1/CIF1 and NMEA2/CIF2 ports is for factory use. The
result is always NG.
SIO TEST
TRX = OK
PORT1 = NG
PORT2 = NG
NMEA2/CIF2 port check
NMEA1/CIF1 port check
CN-A1 port check
PRESS [MENU] KEY TO EXIT
PORT 1/2: FACTORY USE ONLY
SIO test