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Operating Instructions
When COM2 is configured for RS-485 operation the port uses the same female DB-
9 connector on the back of the instrument as when Com2 is configured for RS-232
operation, however, the pin assignments are different.
Figure 6-10:
The signal from this connector is routed from the motherboard via a wiring harness
to a 6 -pin connectors on the CPU card, CN5.
Figure 6-11: CPU connector Pin-Outs for COM2 in RS-485 mode.
6.9.4. DTE versus DCE Communication
RS-232 was developed for allowing communications between Data Terminal
Equipment (DTE) and Data Communication Equipment(DCE). Dumb Terminals
always fall into the DTE category while modems are always considered DCE's. The
difference between the two is which pin is assigned the Data Receive function which
is assigned the Data Transmit function. DTE's receive data on pin 2 and transmit
data on pin 3. DCE's receive data on pin 3 and transmit data on pin 2.
118
Female DB-9 (COM2)
(As seen from outside analyzer)
-
RX/TX
+
RX/TX
1
2
6
Back Panel connector Pin-Outs for COM2 in RS-485 mode.
(Located on CPU card)
RX/TX
+
RX/TX
(As seen from inside analyzer)
The DCE/DTE switch has no effect on COM2.
GND
3
4
5
7
8
9
(RS-485)
CN5
-
GND
2
4
6
1
3
5
NOTE:
Model 400E Ozone Analyzer
Instruction Manual
P/N 04316 Rev: B
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