24
MOVIDRIVE
®
PROFIBUS DFP11A
3
The PROFIBUS-DP
Interface
3.5
Sync and Freeze Mode
In addition to the cyclic exchange of data, where the DP master (higher level automation unit)
addresses all slave stations in turn, the DP master also has the ability to send various control com-
mands to all slaves or just a group of slaves (multicast functions). These control commands permit
event-driven synchronization of the DP slaves.
The Sync control command switches the drive inverters into Sync Mode, for example. The active
setpoints are frozen when in this mode. The DP master now has enough time to send the new
process output data (setpoints) to those stations currently in Sync mode.
When a new Sync command is issued, all drive inverters simultaneously update their active set-
points with the value temporarily stored beforehand. In other words, the active setpoints are not
updated until the new Sync command has been received. The drive inverters quit Sync mode when
the Unsync control command is issued.
The Freeze control command switches the addressed slaves into Freeze Mode. The present status
of the inputs (actual values) is frozen when in this mode.
The master now has enough time to retrieve all the actual values from the drive inverters. When a
new Freeze command is received, all addressed drive inverters simultaneously save their current
actual values (temporarily). The drive inverters quit Freeze mode when the Unfreeze control com-
mand is issued.
3.6
Control via PROFIBUS-DP
The drive inverter is controlled via the process data channel, which can be one, two or three I/O
words in length. These process data words are, for example when a programmable logic controller
is being used as DP master, stored in the I/O or peripheral area of the control system and can thus
be addressed in the usual manner (Fig. 22).
While the process input data (actual values) are being read, e.g. using the Load command in the
case of Simatic S5, the process output data (setpoints) can be sent using the Transfer commands.
Referring to Fig. 22, Example 1 shows the syntax for handling the process input and output data of
the MOVIDRIVE
®
drive inverter. The factory setting for the process data channel is shown as a
comment.
Example: Controlling the drive inverter via the process data
L IW 50
L IW 52
L IW 54
Load PD1 (status word 1)
Load PD2 (speed actual value)
Load PD3 (no function)
L KH 0006
T OW 50
Write 6hex to PD1 (control word 1 = enable)
L KF +1500
T OW 52
Write 1500 dec to PD2 (speed setpoint = 300 rpm)
L KH 0000
T OW 54
Write 0 hex to PD3 (no function, sent value without effect