Siemens SIMATIC S7 System Manual page 558

Libraries
9.5 USS library
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 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.
Table 9- 37
Parameter
XMT_REQ
(transmit re-
quest)
EEPROM
Drive
Param
Index
Value
DB_Ptr
Done
Error
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. The "Error" output is not valid
until the "Done" output turns on.
558
USS_WPM_x parameter descriptions
Description
When ON, a USS_WPM_x request is transmitted to the drive on every scan.
This input enables writing to both RAM and EEPROM of the drive when it is on and
only to the RAM when it is off.
Address of the drive to which the USS_WPM_x command is to be sent. Valid ad-
dresses of individual drives are 0 to 31.
Parameter number
Index value of the parameter that is to be written
Parameter value to be written to the RAM in the drive.
The address of a 16-byte buffer must be supplied to the "DB_Ptr" input. This buffer
is used by the USS_RPM_x instruction to store the results of the command issued
to the drive.
Turned on when the USS_RPM_x instruction completes
This output byte contains the result of executing the instruction. The USS protocol
execution error codes (Page 560) define the error conditions that could result from
executing the instruction.
System Manual, V2.3, 07/2017, A5E03822230-AF
S7-200 SMART