Alstom GEM80-400 Series, Техническое руководство

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GEM80-400 4. Communications
Issue 3 04/99 ALSPA GEM 80-400 SERIES CONTROLLERS TECHNICAL MANUAL Page 4-5
Ports 1, 2 and 3 are configured by presetting data in the P-data table, and then
entering a RECOMPILE command (powering down is not required). The type of
serial port is determined by the value entered in P11 for Port 1, P31 for Port 2 or
P51 for Port 3, and the function of the rest of the P-table locations is dependant
upon this value. The signalling (baud) rate is user defined between 110 and
19,200 bits per second. The rate is selected by entering the baud rate in P10, P30
or P50 for Ports 1, 2 and 3 respectively. The following values of baud rate are
allowed within the limits given in Tables 4.2 to 4.5: 110; 300; 600; 1,200; 2,400;
4,800; 9,600 and 19,200.
If a baud rate other than the above is selected then the controller defaults to
9600 baud with a timeout value of 13.75 seconds
4.3.
Serial Link Communication System
Communications can be established by Point-to-Point Serial Link, where RS232 is
recommended provided that the distance does not exceed the maximum
allowed by the RS232 specification, or Multi-drop Serial Link, where RS485 is the
recommended signal.
4.3.1. Point-to-Point Serial Link
A point-to-point serial link between two controllers may be implemented using
RS232 or RS485. The serial communication port of one controller is set up as a
control port and the other as a tributary port, see Figure 4.4. The control port is
responsible for controlling all activity on the serial link, and the tributary responds
only when a message inviting a reply is addressed to it. Figure 4.5 shows a
typical example of a point-to-point serial communications link between two GEM
80-400 Controllers (RS232). Up to 128 input and output words can be exchanged
at any one time, and the serial link can be operated in either free-running mode
or user-control mode depending on data set in the control port P-table. For
further information and details relating to modes, see the following sections later
in this chapter, 'Free-Running Mode' and 'User-Control Mode'. A GEM
80-400
Controller acting as a tributary may receive and transmit up to 128 words. The
data that needs to be written into the P-table, and where data arrives and is
transmitted from, for a tributary port, is detailed in the sections 'Operation as an
ESP Tributary Port' and 'Operation as an ESP Control Port', later in this chapter.
Figure 4.4 - Point-to-Point Serial Link
GEM80 -400
CONTROLLER
TRIBUTARY
PORT
GEM80 -400
CONTROLLER
CONTROL
PORT