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377
Remote end data communication
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Optical connection of multiplexer is only possible if the multiplexer is of type
FOX6Plus or FOX20 from ABB. The terminal can then be connected optically to the
multiplexer, provided the protection is equipped with the optical fibre modem , not the
short range fibre optical modem, and the FOX is equipped with an Optical Terminal
Module of type N3BT.
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The Remote end data communication consists of two parts, one software part that han-
dles the message structure, packing different pieces together, activate sending of the
messages, unpacking received messages etc, and one hardware part forming the inter-
face against external communication equipments. The hardware part, or built-in mo-
dems, can have either galvanic or optical connection. To ensure compatibility with a
wide range of communication equipment and media, the terminal is designed to work
within the signalling bandwidth of a standard CCITT PCM channel at 64 kbits/s. To en-
able the use in North American EIA PCM systems working at 56 kbits/s, some of the
interfacing modules can be adapted to this bit rate.
The message is based on the HDLC protocol. This is a protocol for the flow manage-
ment of the information on a data communication link that is widely used. The basic
information unit on an HDLC link is a frame. A frame consists of:
•
start (or opening) flag
•
address and control fields (if included)
•
data to be transmitted
•
CRC word
•
end (or closing) flag.
The start and stop flags are 8 bit each and the Cyclic Redundancy Check (CRC) 16 bits.
The data field differs if between a message sent from a slave to a master and a message
sent from a master to a slave. The principle design is according to figure 200 "Data mes-
sage structure" on page 377.
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Start
flag
Information
CRC
Stop
flag
8 bits
n x 16 bits
8 bits
16 bits
Содержание REO 517
Страница 10: ... RQWHQWV ...
Страница 16: ...6 Introduction to the application manual KDSWHU QWURGXFWLRQ ...
Страница 64: ...54 Blocking of signals during test KDSWHU RPPRQ IXQFWLRQV ...
Страница 88: ...78 Scheme communication logic ZCOM KDSWHU LQH LPSHGDQFH ...
Страница 100: ...90 Time delayed phase and residual overcurrent protection TOC1 KDSWHU XUUHQW Equation 36 Iset IsSEC I1b 100 ...
Страница 146: ...136 Unbalance protection for capacitor banks TOCC KDSWHU XUUHQW ...
Страница 166: ...156 Dead line detection DLD KDSWHU 3RZHU V VWHP VXSHUYLVLRQ ...
Страница 171: ...161 About this chapter KDSWHU RQWURO KDSWHU RQWURO ERXW WKLV FKDSWHU This chapter describes the control functions ...
Страница 293: ...283 About this chapter KDSWHU RJLF KDSWHU RJLF ERXW WKLV FKDSWHU This chapter describes the logic functions ...
Страница 378: ...368 Monitoring of DC analog measurements KDSWHU 0RQLWRULQJ ...
Страница 379: ...369 About this chapter KDSWHU 0HWHULQJ KDSWHU 0HWHULQJ ERXW WKLV FKDSWHU This chapter describes the metering functions ...
Страница 384: ...374 Pulse counter logic PC KDSWHU 0HWHULQJ ...
Страница 412: ...402 Serial communication modules SCM KDSWHU DWD FRPPXQLFDWLRQ ...
Страница 440: ...430 LED indication module KDSWHU DUGZDUH PRGXOHV ...