Applies To:
  • CitectSCADA 5.xx, 6.xx
  • CitectHMI 5.xx, 6.xx


How do you set up EXCOM communications to an ABB Advant Controller 450?



The AC450 supports RS-232 communications using the EXCOM protocol (Citect ASEA protocol). Follow these steps to configure it:

1. Install a CI531 serial card in a submodule carrier card (SC510 or SC520) in the AC450 rack.

2. Create an RS232 interface database element to configure the card and its ports. The following settings were used successfully. The bus, station, position, and subposition should be changed to reflect the location of the card:

RS232 interface
BUS:         0
STATION:     0
SUBPOS:      2
IMPL:        1
SERVICE:     1
TYPE:        CI531
CH1:         XCOM_1
CH2:         (unused)


3. Create an ExCom database element to configure the serial port to be used (CH1 or CH2):

NAME:        XCOM_1
ACT:         1
SPEED:       9600
CHLEN:       7

4. Data sets must be created for any data that Citect needs to write to:

Data Set
ACT:         1
IDENT:       -1 (must be a number from -1 to -127)
NO_BREC:     6  (number of digitals desired)
NO_INT:      0  (number of integers desired)
NO_INTL:     0  (number of longs desired)
NO_REAL:     16 (number of reals desired)
USER:        2

5. Set up communications and variable tags in Citect according to the ASEA Masterpiece help pages. See Citect Help | Driver Help | Contents tab | I/O Devices | ABB | ASEA Masterpiece. The listed communication cables or a standard 9-pin null-modem female-female cable may be used.

6. According to the ASEA protocol help, it is also necessary to set this Citect.ini parameter when using a COM port:


Citect can read digital and analog inputs and data sets, but it can only write to data sets configured as shown above. If Citect tries to write to any variables other than data sets as described above, it will display communications error: 0x18 -- Data type from server unknown to driver. When Citect tries to read a new data set created as described above, it may display error: 0x28 -- Bad Response from PLC. To correct this, initialize the variables by writing a value to each one from Citect.

See Q3003 for other available communication methods.

Reference: ABB EXCOM Users Guide (article number 3BSE003835R0001)