Siemens SIMATIC S7-200 System Manual page 349

USS_CTRL Instruction
The USS_CTRL (port 0) or USS_CTRL_P1 (port 1)
instruction is used to control an active MicroMaster drive.
The USS_CTRL instruction places the selected commands
in a communications buffer, which is then sent to the
addressed drive (Drive parameter), if that drive has been
selected in the Active parameter of the USS_INIT
instruction.
Only one USS_CTRL instruction should be assigned to
each drive.
Some drives report speed only as a positive value. If the
speed is negative, the drive reports the speed as positive
but reverses the D_Dir (direction) bit.
The EN bit must be on to enable the USS_CTRL
instruction. This instruction should always be enabled.
RUN (RUN/STOP) indicates whether the drive is on (1) or
off (0). When the RUN bit is on, the MicroMaster drive
receives a command to start running at the specified speed
and direction. In order for the drive to run, the following must
be true:
Drive must be selected as Active in USS_INIT.
-
OFF2 and OFF3 must be set to 0.
-
Fault and Inhibit must be 0.
-
When RUN is off, a command is sent to the MicroMaster
drive to ramp the speed down until the motor comes to a
stop. The OFF2 bit is used to allow the MicroMaster drive to
coast to a stop. The OFF3 bit is used to command the
MicroMaster drive to stop quickly.
The Resp_R (response received) bit acknowledges a response from the drive. All the Active
drives are polled for the latest drive status information. Each time the S7-200 receives a response
from the drive, the Resp_R bit is turned on for one scan and all the following values are updated.
The F_ACK (fault acknowledge) bit is used to acknowledge a fault in the drive. The drive clears
the fault (Fault) when F_ACK goes from 0 to 1.
The DIR (direction) bit indicates in which direction the drive should move.
Table 11-3 Parameters of the USS_CTRL Instruction
Inputs/Outputs
RUN, OFF 2, OFF 3, F_ACK, DIR
Resp_R, Run_EN, D_Dir, Inhibit,
Fault
Drive, Type
Error
Status
Speed_SP
Speed
Using the USS Protocol Library to Control a MicroMaster Drive
Data Types Operands
BOOL I, Q, M, S, SM, T, C, V, L, Power Flow
BOOL I, Q, M, S, SM, T, C, V, L
BYTE VB, IB, QB, MB, SB, SMB, LB, AC, *VD, *AC, *LD,
Constant
BYTE VB, IB, QB, MB, SB, SMB, LB, AC, *VD, *AC, *LD
WORD VW, T, C, IW, QW, SW, MW, SMW, LW, AC, AQW, *VD,
*AC, *LD
REAL VD, ID, QD, MD, SD, SMD, LD, AC, *VD, *AC, *LD,
Constant
REAL VD, ID, QD, MD, SD, SMD, LD, AC, *VD, *AC, *LD
Chapter 11
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