ABB RELION 670 Series Technical Manual page 1335

1MRK 502 066-UUS B
A maximum of 100 meter of cable is allowed to ensure the quality of the data (deviation from X.21
standard cable length).
Synchronization
The X.21 LDCM works like a DTE (Data Terminal Equipment) and is normally expecting
synchronization from the DCE (Data Circuit Equipment). The transmission is normally
synchronized to the Signal Element Timing signal when a device is a DTE. When the signal is high it
will read the data at the receiver and when the signal is low it will write data to the transmitter.
This behaviour can be inverted in the control register.
Normally an external multiplexer is used and it should act like the master.
When two X.21 LDCM is directly communicating with each other one must be set as a master
generating the synchronization for the other (the slave). The DTE Signal Element Timing is created
from the internal 64 kHz clock.
The Byte Timing signal is not used in ABB devices.
22.2.16.4 Technical data
Table 1042:Galvanic X.21 line data communication module (X.21-LDCM)
Quantity
Connector, X.21
Connector, ground selection
Standard
Communication speed
Insulation
Maximum cable length
22.2.17 GPS time synchronization module (GTM)
22.2.17.1 Introduction
This module includes a GPS receiver used for time synchronization. The GTM has one SMA contact
for connection to an antenna. It also includes an optical PPS ST-connector output.
22.2.17.2 Design
The GTM is a PCMIP-format card and is placed only on one of the ADM slots. The antenna input
connector is shielded and directly attached to a grounded plate to eliminate the risk of
electromagnetic interference.
All communication between the GTM and the NUM is via the PCI-bus. PPS time data is sent from
the GTM to the rest of the time system to provide 1μs accuracy at sampling level. An optical
transmitter for PPS output is available for time synchronization of another relay with an optical
Technical manual
Range or value
Micro D-sub, 15-pole male, 1.27 mm (0.050") pitch
2 pole screw terminal
CCITT X21
64 kbit/s
1 kV
100 m
Section 22
IED hardware
GUID-83EC40D0-ABCF-4292-B3DF-155C3A556B76 v3
IP15586-1 v2
M14851-3 v5
M14856-3 v6
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