Siemens SIMATIC S7-1200 System Manual page 1242

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Communication processor and Modbus TCP

13.7 Legacy USS communication (CM/CB 1241 only)

Parameter and type

When the initial USS_DRV execution occurs, the drive indicated by the USS address

(parameter DRIVE) is initialized in the Instance DB. After this initialization, subsequent

executions of USS_PORT can begin communication to the drive at this drive number.

Changing the drive number requires a CPU STOP-to-RUN mode transition that initializes the

instance DB. Input parameters are configured into the USS TX message buffer and outputs

are read from a "previous" valid response buffer if any exists. There is no data transmission

during USS_DRV execution. Drives communicate when USS_PORT is executed. USS_DRV

only configures the messages to be sent and interprets data that might have been received

from a previous request.

You can control the drive direction of rotation using either the DIR input (Bool) or using the

sign (positive or negative) with the SPEED_SP input (Real). The following table indicates

how these inputs work together to determine the drive direction, assuming the motor is wired

for forward rotation.

Table 13- 123 Interaction of the SPEED_SP and DIR parameters

Drive Current Speed (scaled value of drive status word 2): The value of

the speed of the drive as a percentage of configured speed.

Drive Status Word 1: This value contains fixed status bits of a drive.

Drive Status Word 3: This value contains a user-configurable status

word on the drive.

Drive Status Word 4: This value contains a user-configurable status

word on the drive.

Drive Status Word 5: This value contains a user-configurable status

word on the drive.

Drive Status Word 6: This value contains a user-configurable status

word on the drive.

Drive Status Word 7: This value contains a user-configurable status

word on the drive.

Drive Status Word 8: This value contains a user-configurable status

word on the drive.

Drive rotation direction

S7-1200 Programmable controller

System Manual, V4.2, 09/2016, A5E02486680-AK