Serial Communication; Standard Of Communications; Software Characteristics - ABB AW400 Series Instruction Manual

10 SERIAL COMMUNICATION

Note: This section applies only to instruments equipped with the optional Serial Communication P.C. Board.

10.1 Standard of Communications

Two digital communication standard are supported by the serial communication board of AW400, one port is
an RS232 serial interface and the other is an RS 422/485 serial interface. Only one port at a time can be
activated, and the selection of the desired standard is made via software at the Configuration Menu.
The Factory default setting is RS 422/485, which allows up to a maximum of 32 instruments to be connected
to the same Data-link, where each instrument must have a unique address number ranging from 00 to 31
(Factory setting is 00).
The RS 232 standard can be selected for a peer to peer communication mode.
Transmission speed can be adjusted between 1200 and 28800 baud in the Configuration Menu; default
setting is 28800, asynchronous by character.
One character can be defined as either one of the following two modes:
Mode 1 - (Standard PC mode - Default setting by Factory):
1 Start bit;
8 Data Bits – the Least Significant Bit (LSB) is transmitted first;
1 Stop Bit.
Mode 2 - (Optional setting):
1 Start bit;
8 Data Bits – the Least Significant Bit (LSB) is transmitted first;
1 Even Parity bit
1 Stop Bit.
NOTE: When operating in RS232 mode, the character definition must be set as Mode 1.
Mode 2 is active optionally only when operating in RS485.
To modify this selection, enter the Configuration menu and select the RS585 mode: the menu will
ask to select Mode 1 or Mode 2. When Mode 1 is selected and the communication is to work in
RS232, remember to set RS232 again in the menu after having selected "Mode 1" from the
RS485 menu.

10.1.1 Software characteristics

1. All transactions are initiated by the Host: The AW400 can only work as a responder to Host commands
(Interrogate or Change).
2. All AW400 begin their response within 10 ms after the end of the transmission by the Host, otherwise a
faulty transmission may be assumed.
3. The maximum number of data bytes per message is 32 (decimal).
4. Data type are made up of 1 (logical), 2 (integer), 4 (floating point) bytes or string type, with string length
bytes, according to Intel Format.
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