ABB 8241 Operating Instructions Manual page 24

8240 series. modbus communication supplement
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...11 OPERATION
Check that the parameters programmed in the instrument's
computer terminal or host computer – see Section 7.
If communication is still not possible or is erratic, check that the computer terminal, or host computer, interface has pull-up ant
pull-down resistors connected as shown in Figs. 11.1 and 11.2.
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 re-checked.
22
1
2
3
Rx+
Tx+
4
5
6
Rx–
Tx–
Fig. 11.2 Pull-up and Pull-down Resistors (3-wire only)
Serial Data Communication Page
Computer Terminal or Host Computer
Pull-down
Resistor
Tx–
Tx+
Rx–
Rx+
Pull-down
Resistor
0V
are compatible with those of the
'A'
'B'
+5V
Pull-up
Resistor
'A'
'B'

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