Configuring Receive Parameters - Siemens SIMATIC S7 System Manual
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Parameter
Send break at message start
Number of bit times in a
break
Send idle line after a break
Idle line after a break
12.3.3.2
Configuring receive parameters
From the device
configuration, you configure
how a communication
interface receives data, and
how it recognizes both the
start of and the end of a
message. Specify these
parameters in the Receive
message configuration for
the selected interface.
You can also dynamically configure or change the receive message parameters from the
user program by using the RCV_CFG instruction (Page 537).
Note
Parameter values set from the RCV_CFG instruction in the user program override the port
configuration settings. Note that the CPU does not retain parameters set from the RCV_CFG
instruction in the event of power down.
Message start conditions
You can determine how the communication interface recognizes the start of a message. The
start characters and the characters comprising the message go into the receive buffer until a
configured end condition is met.
You can specify multiple start conditions. If you specify more than one start condition, all of
the start conditions must be met before the message is considered started. For example, if
you configure an idle line time and a specific start character, the CM or CB will first look for
the idle line time requirement to be met and then the CM will look for the specified start
character. If some other character is received (not the specified start character), the CM or
CB will restart the start of message search by again looking for an idle line time.
S7-1200 Programmable controller
System Manual, 11/2011, A5E02486680-05
Definition
Specifies that upon the start of each message, a break will be sent after the RTS On delay
(if configured) has expired and CTS is active.
You specify how many bit times constitute a break where the line is held in a spacing
condition. The default is 12 and the maximum is 65535, up to a limit of eight seconds.
Specifies that an idle line will be sent before message start. It is sent after the break, if a
break is configured. The "Idle line after a break" parameter specifies how many bit times
constitute an idle line where the line is held in a marking condition. The default is 12 and
the maximum is 65535, up to a limit of eight seconds.
105BCommunication processor
12.3 Point-to-Point (PtP) communication
553
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