VISTEK V1679 single-mode fibre
data transceiver
HU-V1679
15
4.
SERIAL COMMUNICATION PORTS
4.1
Description
All V1679 models have two independently operating Serial Communication Ports, named COM1 and COM2.
Both ports can be configured to comply either with RS-232 (single-ended) or RS-422 (differential) electrical
standards as specified by the EIA (Electronics Industry Association).
Free and useful RS-232/422/485 publications can be found on Analog Device's website (
www.analog.com
) or
on B&B Electronic's website (
www.bb-elec.com
).
A highly recommended reading on the RS-232 interface standard is Maxim's Application Note 83
'Fundamentals of RS-232 Serial Communications', which can be downloaded from Maxim's website
(
www.maxim-ic.com
).
Mode of operation, slew rate and an optional line termination (RS-422 only) can be configured by setting
Jumpers accordingly.
Data transfer rates of up to 1Mbps in RS-232 mode and 10Mbps in RS-422 mode can be achieved. The
transmission length depends largely on the interface type (RS-232 or RS-422), the quality of the cable and
the data rate itself. In theory, RS-422 can go as far as 4000 ft. @ 10Mbps. The single-ended RS-232
interface is generally speaking less robust and more susceptible to interference than its differential
counterpart RS-422. With RS-232, typical cable lengths at low data rates (9600kbaud) are about 50 ft. In
some cases, with the use of a special, high quality cable, this limit can be extended to as much as 150 ft.
The RS-422 receivers used on the V1679 are equipped with a failsafe circuitry that guarantees a logic high
receiver output when the receiver inputs are open or shorted. Furthermore, receivers and transmitters are
protected against wiring faults.