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Serial communication
interface
Synchronizing of the
blinking sequence
18
The alarm annunciator unit comprises a serial
communication port over which the unit can be
connected to a local reporting and data commu-
nication system using the SPA bus protocol.
The physical connection for the serial interface
is located on the screw terminals on the back of
the unit using terminals 1, 2, 3, 13 and 14 (se
figure 16) The serial interface is according to the
RS 485 standard.
Using electrical connection the transfer distance
is about 20 to 30 m depending on the interfer-
ence level of the installation. The maximum
allowed ground potential difference between
the units is ±10V.
A fiber optical connection module, SPA-ZC 17
or SPA-ZC 21 is used to connect the unit to a
fiber optical bus. The transfer distance using
fiber optical media is approximately 30 m for
plastic fiber and 2 km for glass fiber.
Note! Because of the disturbant environment
(like in substations) where the units are operat-
ing it is always recommended to use fiber optical
communication.
By using the LON/SPA gateway, SPA-ZC 100,
the alarm annunciator might also be connected
to the LON bus.
1
Rx/Tx
2
3
Fig. 16. Principle lay-out of the serial communication interface.
If several units are located close to each other
without any connection to a higher level system,
it might be desired to synchronize the blinking
sequences between the units. This is done by
connecting the serial interfaces together and to
configure one of the units to transmit a synchro-
nizing signal (V201=1) and the others to receive
that signal (V201 = 0).
The SPA bus protocol is described in the docu-
ment SPA bus communication protocol V2.5,
34 SPACOM 2 EN1 and the LON Talk proto-
col is described in the document LON bus -
LON Works network in protection and control
systems; 1MRS750035-MTD EN
The speed of the serial communication is nor-
mally 9600 bits/s
Through the serial communication the follow-
ing information is read from the unit:
- the event registers including the time mark-
ings
- the state of the channels and of the system
- the programmed parameter values
- pulse counter values
The following data can be written to the unit:
- time synchronization
- audible device reset
- alarm channels acknowledge and reset
- control of an alarm channel
- control of output relays
- control of the interlocking channels
- setting values
- testing of the unit
Data direction
Data
on SPA-bus
8V
V201 Setting of transmission rate
0 = 9600 bits/s, synch pulse receiver
1 = 9600 bits/s, synch pulse transmitter
2 = 9600 bits/s
3 = 4800 bits/s
4 = 2400 bits/s
5 = 1200 bits/s
6 = 300 bits/s
13
RTS
14
15
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