Siemens DTU3005-B manual Device Command Registers

4 Creating Project Files—PLC to Devices

parameter is used only with Allen-Bradley PLCs. It specifies the file number in the PLC that contains the register values that are transferred to or from the device.

4.Select Save to save the information to the project file, and then select Ok or press Esc to exit the device diagnostic registers screen. If at any time you want to return to the last saved version of the device diagnos- tics registers, select Revert without saving any changes.

4.11Device Command Registers

The device command registers consist of two consecutive registers for each device entered in the device list. These registers allow the PLC to transmit commands to each of the devices. To send a command, all the PLC needs to do is to place the command values into the appropriate PLC reg- isters, which the DTU3005B unit reads and then processes.

The first register contains the command, and the second register contains the data associated with the command. The format of the command registers for each device are described in Appendix E. All the command registers are placed in contiguous locations in the PLC’s registers and

are assigned by the DTU3005 to each device in the order that they are listed in the device list.

To use the command registers for a particular device, the PLC program must do the following, in order:

1.First, set the command word to 0 or -1 (FFFF hexadec- imal).

2.Set the data word to the appropriate value.

3.Set the command word to the appropriate value.

4.After the command is set the PLC must wait for the DTU3005B unit to change the command word to either 0 (to indicate successful processing of the command), or -1 (to indicate an error).

To indicate the location of the command registers on the PLC, follow these steps:

1.Select Device Command Registers from the Edit menu. The Device Command Registers screen appears:

2.Enter the starting register address in the PLC Regis- ters field. The DTU3005 Editor software will determine the proper number of registers for the number of devices entered in the device list and indicate the final register number. These registers must be different from those used for device data and diagnostics. Refer to Appendix A for a list of valid register numbers for your PLC. Failure to use different register addresses will cause communication errors, and may cause unex- pected operation of the devices.

3.Press Shift+Tab, or click the left mouse button to high- light the File field and enter the file number. This parameter is used only with Allen-Bradley PLCs to specify the file number in the PLC that contains the reg- ister values that are transferred to or from the device.

26 Siemens Energy & Automation, Inc.