TC1710 RS-485
(Optional Dual Optics)
User's Manual
Rev. 1.6
−3−
Chapter 1 - Overview
Description
The TC1710 RS-485 is an economical and dependable fiber optic modem with RS-485 interface (same as
RS-422 with DB25 connector). It is available in either rack mount or stand alone versions; the rack mount
version can be converted to the stand alone version with the addition of a sheet metal box. The TC1710 can
communicate at distances up to 4 km using Multimode optics and up to 80 km using Single Mode optics.
TC1710's design utilizes advanced FPGA (Field Programmable Gate Array) technology to increase reliability
and flexibility.
Electrical Specifications
Interface:
RS-485 Async
Data Rates:
Up to 10Mbps
Connector:
DB25 Female DCE
Theory of Two and Four-Wire RS-485 Operation
Figure 1. Two-Wire RS-485 Logic Diagram
Two-wire RS-485 is a half-duplex operation, which means transmit and receive operations take turns; they
do not function concurrently. From the user’s point-of-view, the channel is in receiving mode when no data
is transmitted from the remote unit. (See Figure 1).
Four-wire RS-485 is a full-duplex operation, which means transmit and receive operations function
concurrently. From the user's point-of-view, both channels are in the receiving or transmitting mode at all
times. (See fFgure 2).
The RS-485 Driver/Receiver transition time is determined by four internal DIP switches (internal SW1) on
the TC1710. The local unit's RS-485 transceiver changes to transmit (Tx) mode upon receiving the first bit
of data from the remote unit. The transition time is the amount of time before the local unit's RS-485
transceiver will revert to the high-impedance receiver mode after the last bit is received from the remote unit.
The RS-485 transition time should be set according to Table 1 on page 6.
Figure 2. Four-Wire RS-485 Logic Diagram