Getting Started P54x/EN GS/La4
MiCOM P543, P544, P545 & P546
(GS) 3-15
SK1
SK2
MiCOM relay
Laptop
Serial communication port
(COM 1 or COM 2)
Serial data connector
(up to 15m)
25 pin
download/monitor port
Battery
9 pin
front comms port
P0107ENb
GS
Figure 6 Front port connection
The relay is a Data Communication Equipment (DCE) device. Therefore the pin connections
of the relay’s 9-pin front port are as follows:
Pin number Description
2 Tx Transmit data
3 Rx Receive data
5 0 V Zero volts common
None of the other pins are connected in the relay. The relay should be connected to the
serial port of a PC, usually called COM1 or COM2. PCs are normally Data Terminal
Equipment (DTE) devices which have a serial port pin connection as below (if in doubt check
your PC manual):
Pin number 25-way 9-way Description
2 3 2 x Receive data
3 2 3 Tx Transmit data
5 7 5 0 V Zero volts common
For successful data communication, the Tx pin on the relay must be connected to the Rx pin
on the PC, and the Rx pin on the relay must be connected to the Tx pin on the PC, as shown
in Figure 7. Therefore, providing that the PC is a DTE with pin connections as given above,
a ‘straight th
rough’ serial connector is required, i.e. one that connects pin 2 to pin 2, pin 3 to
pin 3, and pin 5 to pin 5.
Note: A common cause of difficulty with serial data communication is
connecting Tx to Tx and Rx to Rx. This could happen if a ‘cross-over’
serial connector is used, i.e. one that connects pin 2 to pin 3, and pin
3 to pin 2, or if the PC has the same pin configuration as the relay.
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