Modbus TCP interface

Address

Description

0x0000
0x00FF

Process data interface
Inputs

0x0800
0x08FF

Process data interface
Outputs

0x1000
0x1006

Read only

Bus Coupler identification

0x100A

2 byte PLC interface

0x100B

Bus terminal diagnosis

0x100C

Bus Coupler status

0x1010

Process image length in bits, analog outputs (without PLC variables)

0x1011

Process image length in bits, analog inputs (without PLC variables)

0x1012

Process image length in bits, digital outputs

0x1013

Process image length in bits, digital inputs

0x1020

Watchdog, current time in [ms]

0x110A

Read / Write

2 byte PLC interface

0x110B

Bus terminal diagnosis

0x1120

Watchdog, pre-defined time in [ms] (Default value: 1000)

0x1121

Watchdog reset register

0x1122

Type of watchdog

1

Telegram watchdog (default)

0

Write telegram watchdog

0x1123**

ModbusTCP mode**

1

Fast Modbus

0

Normal Modbus (default)

0x4000*
0x47FF

Flags area (%MB..)*

* all Bus Terminal controllers BC9xx0 and BX9000
** for BC9x00 from firmware B7 and BK9000 from firmware B5 and all unlisted BK9xxx and BC/BX9xxx

Watchdog

The watchdog is active under the factory settings. After the first write telegram the watchdog timer is initiated, and is triggered each time a telegram is received from this device. Other devices have no effect on the watchdog. A second approach, which represents a more sensitive condition for the watchdog, is for the watchdog only to be re-triggered after each write telegram. To do this, write a zero into register 0x1122 (default value "1").
The watchdog can be deactivated by writing a zero to offset 0x1120. The watchdog register can only be written if the watchdog is not active. The data in this register is retained.

Watchdog register

If the watchdog timer on your slave has elapsed it can be reset by writing twice to register 0x1121. The following must be written to the register: 0xBECF 0xAFFE. This can be done either with function 6 or with function 16.

The Bus Coupler's status register

Bit

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Name

FB

-

-

-

-

-

-

-

-

-

-

-

-

-

CNF

KB

Legend

Bit

Name

Value

Description

15

FB

1bin

Fieldbus error, watchdog time elapsed

14...2

-

-

reserved

1

CNF

1bin

Bus Coupler configuration error

0

KB

1bin

Bus Terminal error

ModbusTCP mode

The fast Modbus mode should only be used in small local networks. The fast ModbusTCP is not active under the default settings. If problems are found to occur with this type of communication, the Bus Coupler should be switched to "normal" ModbusTCP communication. The mode is set in the Modbus interface, offset 0x1123. It is necessary to reset the coupler (e.g. using ModbusTCP function 8) after the change. It is not permitted to send more than one Modbus service within one Ethernet frame in fast Modbus mode.

2 byte PLC interface

Registers in the complex terminals and Bus Terminal Controller registers can be both read and written using the 2 byte PLC interface. The complex terminal registers are described in the associated terminal documentation. The Bus Coupler registers can be used, for example, to read terminal bus diagnostics data, the terminal composition or the cycle times, and the programmed configuration can be written. It is also possible for a manual K-bus reset to be carried out. The 2-byte PLC interface requires two bytes each of input and output data. They are handled using a special protocol. A description of the 2 byte PLC interface, the registers available in the Bus Couplers and of function blocks for various PLC systems that support the 2 byte PLC interface can be supplied on request.

2 byte diagnostic interface

The terminals' error messages can be sent over the 2-byte diagnostic interface. K-bus diagnostics must however be activated for this purpose. The 2-byte diagnostic interface occupies two bytes each of input and output data. A special protocol is processed via these two bytes. A description of the 2 byte-diagnostic interface can be supplied on request.