23
9 OPERATION
Before attempting any serial communication,
first ensure that the C300 Controllers
connected to the computer terminal or host
computer by serial link are functioning
correctly as individual instruments. This is
achieved by connecting all analogue inputs,
applying the input signals and checking that
the digital display reads appropriately.
Ensure that the serial data connections to
C300 Controller have been made correctly
with respect to the computer terminal, or host
computer, interface. If the above check
appears satisfactory, test the serial
communication by sending an appropriate
message from the computer terminal or host
computer to a controller and observe if it
replies; thus establishing communication. If
communication is not established, check that
the computer terminal, or host computer,
interface is correctly set up and that the plug-
in links within each controller are correctly
positioned – see Section 5 on page 4.
Check that the parameters programmed in
the instrument’s Serial Data Communication
Page are compatible with those of the
computer terminal or host computer – see
Section 7 on page 5.
If communication is still not possible or is
erratic, check that the computer terminal, or
host computer, interface has pull-up and
pull-down resistors connected as shown in
Fig. 9.1.
✶
Note. If no reply is received from
the instrument within 160ms, retransmit
the command. If after five command re-
entries a satisfactory reply has not been
received, the communication link has
been broken and must be rechecked –
see above.
8
9
10
11
12
Common
Rx+
Rx–
Tx+
Tx–
ABC
C
+5V
+5V
0V
0V
Pull-up
Resistor
Pull-up
Resistor
Pull-down
Resistor
Pull-down
Resistor
Computer Terminal or Host Computer
C300 Controller
Fig. 9.1 Pull-up and Pull-down Resistors
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