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MICROgarde controller I and II
04.20.11.18
2.4.6
Communications
Earthing
The communications cable should be earthed on the incoming side only: the cable bringing
communications in from the administration computer or the preceding MICROgarde unit or
other Access Control Unit (ACU). The communications cable leaving the ACU should ideally
be taped off. (This prevents earth loops).
For RS485 termination, put the termination dip switches 1 and 2 ON. Do this only on the first
MICROgarde controller in the RS485 bus.
RS232 communication
Note.
This method is only suitable if the administration PC is within 15m of the MICROgarde unit
and has a vacant COM port. If the administration PC is more than 15m from a MICROgarde unit
and you want to use RS232, you will need to use an RS232/RS485 converter. The TDSI RS232
to 2-wire RS485 Converter can be used for this purpose – part no. 5012-0013 (UK plug) or 5012-
0014 (Euro Plug).
Create an RS232 link as described in Table 2 and shown in Figure 10.
Networking a PC to a MICROgarde using RS232
RS232 Pin
MICROgarde pin
Colour*
2
2 – RS232 Tx
Red
3
1 – RS232 Rx
Blue
5
3 - 0V
Green
*TDSi RS232 comms lead (5002-1813) only.
Other manufacturers may use different colour coding.
To create a network, you can connect further MICROgarde units from connections 4 & 5.
These connections use RS485 but the MICROgarde has a built-in RS485/RS232 conversion
capability. Up to a maximum of 31 MICROgarde controllers can be added in this way.
Ensure you use a continual line or “daisy chain” with no spurring.
Note.
4-core RS485 cable is often cheaper and more easily obtained than 2-core. If you use 4-
core cable, connect the cores together in pairs, using one core from each pair – do not leave
cores un-connected.
RS232 communication: first controller within 15m of PC
RS232 communication: first controller more than 15m from PC