4
Creating Project Files—PLC to Devices
26
Siemens Energy & Automation, Inc.
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.
4.11
Device 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.
