Siemens SIMATIC S7-200 System Manual page 353

USS_WPM_x Instruction
There are three write instructions for the USS protocol:
USS_WPM_W (port 0) or USS_WPM_W_P1 (port 1)
-
instruction writes an unsigned word parameter.
USS_WPM_D (port 0) or USS_WPM_D_P1 (port 1)
-
instruction writes an unsigned double word parameter.
USS_WPM_R (port 0) or USS_WPM_R_P1 (port 1)
-
instruction writes a floating-point parameter.
Only one read (USS_RPM_x) or write (USS_WPM_x)
instruction can be active at a time.
The USS_WPM_x transactions complete when the
MicroMaster drive acknowledges receipt of the command,
or when an error condition is posted. The logic scan
continues to execute while this process awaits a response.
The EN bit must be on to enable transmission of a request,
and should remain on until the Done bit is set, signaling
completion of the process. For example, a USS_WPM_x
request is transmitted to the MicroMaster drive on each
scan when XMT_REQ input is on. Therefore, the XMT_REQ
input should be pulsed on through an edge detection
element which causes one request to be transmitted for
each positive transition of the EN input.
The EEPROM input enables writing to both RAM and
EEPROM of the drive when it is on and only to the RAM
when it is off. Note that this function is not supported by
MM3 drives, so this input must be off.
The Drive input is the address of the MicroMaster drive to
which the USS_WPM_x command is to be sent. Valid
addresses of individual drives are 0 to 31.
Param is the parameter number. Index is the index value of
the parameter that is to be written. Value is the parameter
value to be written to the RAM in the drive. For MicroMaster
3 drives, you can also write this value to the EEPROM of the
drive, based on how you have configured P971 (EEPROM
Storage Control).
The address of a 16-byte buffer must be supplied to the DB_Ptr input. This buffer is used by the
USS_WPM_x instruction to store the results of the command issued to the MicroMaster drive.
When the USS_WPM_x instruction completes, the Done output is turned on and the Error output
byte contains the result of executing the instruction. Table 11-6 defines the error conditions that
could result from executing the instruction.
When the EEPROM input is turned on, the instruction writes to both the RAM and the EEPROM of
the drive. When the the input is turned off, the instruction writes only to the RAM of the drive.
Because the MicroMaster 3 drive does not support this function, you must ensure that this input is
off in order to use this instruction with a MicroMaster 3 drive.
Table 11-5 Valid Operands for the USS_WPM_x Instructions
Inputs/Outputs Data Type
XMT_REQ BOOL
EEPROM BOOL
Drive BYTE
Param, Index WORD
DB_Ptr DWORD
Value WORD
DWORD, REAL
Using the USS Protocol Library to Control a MicroMaster Drive
Operands
I, Q, M, S,SM,T,C,V,L, Power Flow conditioned by a rising edge detection element
I, Q, M, S, SM, T, C, V, L, Power Flow
VB, IB, QB, MB, SB, SMB, LB, AC, *VD, *AC, *LD, Constant
VW, IW, QW, MW, SW, SMW, LW, T, C, AC, AIW, *VD, *AC, *LD, Constant
&VB
VW, IW, QW, MW, SW, SMW, LW, T, C, AC, AQW, *VD, *AC, *LD
VD, ID, QD, MD, SD, SMD, LD, *VD, *AC, *LD
Chapter 11
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