Two-Channel Two-Clock Rs422 Interface; Rs422 And Fiber Interface - GE N60 Instruction Manual

3 HARDWARE
d) RECEIVE TIMING
The RS422 interface utilizes NRZI-MARK modulation code and; therefore, does not rely on an Rx clock to recapture data.
NRZI-MARK is an edge-type, invertible, self-clocking code.
To recover the Rx clock from the data-stream, an integrated DPLL (digital phase lock loop) circuit is utilized. The DPLL is
driven by an internal clock, which is 16-times over-sampled, and uses this clock along with the data-stream to generate a
data clock that can be used as the SCC (serial communication controller) receive clock.
The two-channel two-clock RS422 interface (module 7V) is for use with the synchrophasor feature. The figure shows the
module connections.
Figure 3–39: TWO-CHANNEL TWO-CLOCK RS422 INTERFACE CONNECTIONS
The following figure shows the combined RS422 plus Fiber interface configuration at 64K baud. The 7L, 7M, 7N, 7P, and 74
modules are used in two-terminal with a redundant channel or three-terminal configurations where channel 1 is employed
via the RS422 interface (possibly with a multiplexer) and channel 2 via direct fiber.
AWG 24 twisted shielded pair is recommended for external RS422 connections and the shield should be grounded only at
one end. For the direct fiber channel, power budget issues should be addressed properly.
When using a laser interface, attenuators may be necessary to ensure that you do not exceed maxi-
mum optical input power to the receiver.
Connections shown above are for multiplexers configured as DCE (data communications equipment) units.
GE Multilin N60 Network Stability and Synchrophasor Measurement System
1a
~
1b
~
~ 2b
COM
~ 2a
Tx1 +
~ 3a
Rx1 –
~ 3b
Tx1 –
~ 4b
Rx1 +
~ 6a
Shield
Tx2 Rx2
~ 8a
Figure 3–40: RS422 AND FIBER INTERFACE CONNECTION
3.3 DIRECT INPUT AND OUTPUT COMMUNICATIONS

3.3.6 TWO-CHANNEL TWO-CLOCK RS422 INTERFACE

3.3.7 RS422 AND FIBER INTERFACE

Clock
(channel 1)
RS422
channel 1
Fiber
channel 2
Surge
842777A1.CDR
3
3-35