105BCommunication processor
12.4 Universal serial interface (USS) communication
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
573
12.4.3
USS_PORT instruction
Table 12- 38 USS_PORT instruction
LAD / FBD
SCL
Description
USS_PORT(
PORT:=_uint_in_,
BAUD:=_dint_in_,
ERROR=>_bool_out_,
STATUS=>_word_out_,
USS_DB:=_fbtref_inout_);
The USS_PORT instruction handles communication
over a USS network.
Table 12- 39 Data types for the parameters
Parameter and type
Data type
Description
PORT
IN
Port
After you install and configure a CM or CB communication device, the
port identifier appears in the parameter helper drop-list available at the
PORT box connection. The assigned CM or CB port value is the device
configuration property "hardware identifier". The port symbolic name is
assigned in the "System constants" tab of the PLC tag table.
BAUD
IN
DInt
The baud rate used for USS communication.
USS_DB
INOUT
USS_BASE
The name of the instance DB that is created and initialized when a
USS_DRV instruction is placed in your program.
ERROR
OUT
Bool
When true, this output indicates that an error has occurred and the
STATUS output is valid.
STATUS
OUT
Word
The status value of the request indicates the result of the scan or
initialization. Additional information is available in the
"USS_Extended_Error" variable for some status codes.
Typically, there is only one USS_PORT instruction per PtP communication port in the
program, and each call of this function handles a transmission to or from a single drive. All
USS functions associated with one USS network and PtP communication port must use the
same instance DB.
Your program must execute the USS_PORT instruction often enough to prevent drive
timeouts. USS_PORT is usually called from a cyclic interrupt OB to prevent drive timeouts
and keep the most recent USS data updates available for USS_DRV calls.
