AD-AAB 20 GX

The AD-AAB 20 GX contains a RS485 bus interface on which the Modbus RTU protocol is used. All control functions of the device can be executed via this bus interface. The preset standard data format is 19200,e,8,1. Adaptation to a different data format is possible at any time. The bus address (1...99) is set to the side-mounted rotary switches. The address 0 is not permitted for the bus operation. However, on this zero position the device is accessible only via the standard data format (19200, e, 8.1). The position 0 thus represents a service position, the example can be used during parameterization error.

The AD-AAB 20 GX supports two Modbus functions. These are the functions "Read Holding Registers" (0x03) and "Write Holding Registers" (0x10). With the "Read Holding Registers" function data can be read from the device and written with "Write Holding Registers" data. The individual register width is 16 bits. Please see the Modbus specification for detailed explanations of the Modbus communication. This is online available for free and can be downloaded from the Adamczewski homepage.

The following Modbus data are accessible via the RS485 bus:

Start address	Reg. number	Name	Datatype	[Code] = Value	read	write
40501	1	Address switch	U16	1...99...247	yes	yes
40502	1	Flashing function	U16	0/1...255	yes	yes
40901	2	Analog output U1	FLOAT	0...10V	no	yes
40903	2	Analog output I1	FLOAT	0...20mA	no	yes
40905	2	Analog output U2	FLOAT	0...10V	no	yes
40907	2	Analog output I2	FLOAT	0...20mA	no	yes
40909	2	Scale out U1	FLOAT	+/- Scale value	no	yes
40911	2	Scale out I1	FLOAT	+/- Scale value	no	yes
40913	2	Scale out U2	FLOAT	+/- Scale value	no	yes
40915	2	Scale out I2	FLOAT	+/- Scale value	no	yes
44201	2	Scale begin Channel 1	FLOAT	+/- Scale range	yes	yes
44203	2	Scale begin Channel 2	FLOAT	+/- Scale range	yes	yes
44205	2	Analog begin Channel 1	FLOAT	0...100 %	yes	yes
44207	2	Analog begin Channel 2	FLOAT	0...100 %	yes	yes
44211	2	Scale end Channel 1	FLOAT	+/- Scale range	yes	yes
44213	2	Scale end Channel 2	FLOAT	+/- Scale range	yes	yes
44215	2	Analog end Channel 1	FLOAT	0...100 %	yes	yes
44217	2	Analog end Channel 2	FLOAT	0...100 %	yes	yes
42901	1	Baud rate	U16	Index, see list below	yes	yes
42902	1	Parity	U16	[0]=even; [1]=odd; [2]=no	yes	yes
42903	1	Modbus Master	U16	0/1	yes	yes
49102	1	Device reset	U16	0	no	yes
49105	6	Device type	String	AAB20GX	yes	no
49119	1	Firmware version	U16	MSB/LSB	yes	no

Coding baudrate list

index	0	1	2	3	4	5	6	7	8	9
baud	2400	4800	9600	14400	19200	28800	38400	57600	76800	115200

After changing the interface parameters, a device reset is required.

Modbus master mode
The device can even work in Modbus master mode to transfer data between any devices within an RS485 line.
For Modbus master operation, starting with Modbus register 40611, there are 37 consecutive data transfer sets,
with 5 configuration registers each.

Start address	Reg. number	Name	Datatype	[Code] = Value	read	write
40611	1	Source address [1]	U16	1...98	ja	ja
40612	1	Source register [1]	U16	nnnnn	ja	ja
40613	1	Target address [1]	U16	1...99	ja	ja
40614	1	Target register [1]	U16	nnnnn	ja	ja
40615	1	Register count [1]	U16	1/2	ja	ja
40791	1	Source address [37]	U16	1...98	ja	ja
40792	1	Source register [37]	U16	nnnnn	ja	ja
40793	1	Target address [37]	U16	1...99	ja	ja
40794	1	Target register [37]	U16	nnnnn	ja	ja
40795	1	Register count [37]	U16	1/2	ja	ja

For the Modbus master mode, the parameter "Modbus master" must be activated and the address switch set to position 99.
Data transfer begins six seconds after activation or device restart.
A flashing green LED indicates a communication error.