ABB 4620 User Manual page 25

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 and
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.
TBA
Common
Rx–
Rx+
Tx–
Tx+
or
1
4
Tx+
Channel 1 Channel 2
TBB
4600 Transmitter
(Panel Mounted)
1
2
3
4
5
2 3
Rx+ Rx–
5 6
Tx– 0V
4600 Transmitter
(Wall Mounted)
Serial
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
11 OPERATION
are compatible with those of the
'A'
'B'
+5V
Pull-up
Resistor
'A'
'B'
23