
VISTEK V1679 single-mode fibre
data transceiver
HU-V1679
17
4.2.1
RS-232/422 Mode Selection Jumper
The Mode Selection Jumper is used to configure a port for RS-232 or RS-422 operation. The following
combinations are supported:
COM1: RS-232 RxD/TxD, CTS/RTS
COM2: RS-232 RxD/TxD, CTS/RTS
COM1: RS-422 RxD/TxD only
1
COM2: RS-422 RxD/TxD only
1
COM1: RS-232 RxD/TxD, CTS/RTS
COM2: RS-422 RxD/TxD only
1
COM1: RS-422 RxD/TxD only
1
COM2: RS-232 RxD/TxD, CTS/RTS
COM1: RS-232 full Modem support (RxD/TxD, CTS/RTS, DSR/DTR)
2
COM2: RS-232 RxD/TxD only
1
Notes:
1. 'RxD/TxD only' means data transfer without hardware flow control (i.e. no CTS/RTS, DSR/DTR status
lines). Data protocol must support e.g. Xon/Xoff scheme for high data rates.
2. For full Modem support, two control lines (DSR/DTR) are actually 'borrowed' from COM2. In this mode,
COM2 can only operate as RS-232 with RxD/TxD lines only.
Factory default setting is RS-232 for COM1 and COM2.
4.2.2
Slew-rate Selection Jumper (Slow/Fast)
Slew-rate limiting (set Jumper to 'Slow') minimizes EMI and reduces reflections caused by improperly
terminated cables, allowing error-free data transmission up to 250kbps. Disabling slew-rate limiting (set
Jumper to 'Fast') allows the Transceiver to transmit at data rates up to 10Mbps in RS-422 mode and up to
1Mbps in RS-232 mode. Factory default setting is 'Slow' for COM1 and COM2.
4.2.3
Line Termination Jumper (RS-422 Only)
At data rates higher than 250kbps, is strongly recommended to terminate the RxD line pair in RS-422 mode
by shorting the 'Term' Jumper.
Note that the Termination Jumper must not be installed when a port is configured as RS-232.
Factory default setting is 'No Termination' for COM1 and COM2.