105BCommunication processor
12.3 Point-to-Point (PtP) communication
S7-1200 Programmable controller
552
System Manual, 11/2011, A5E02486680-05
Software flow control requires full-duplex communication, as the receiving partner must be
able to send XOFF to the transmitting partner while a transmission is in progress. Software
flow control is only possible with messages that contain only ASCII characters. Binary
protocols cannot utilize sofware flow control.
12.3.3
Configuring the transmit (send) and receive parameters
Before the CPU can engage in PtP communications, you must configure parameters for
transmitting (or sending) messages and receiving messages. These parameters dictate how
communications operate when messages are being transmitted to or received from a target
device.
12.3.3.1
Configuring transmit (send) parameters
From the device
configuration, you configure
how a communication
interface transmits data by
specifying the "Configuration
of transmitted message"
properties for the selected
interface.
You can also dynamically configure or change the transmit message parameters from the
user program by using the SEND_CFG (Page 535) instruction.
Note
Parameter values set from the SEND_CFG instruction in the user program override the port
configuration settings. Note that the CPU does not retain parameters set from the
SEND_CFG instruction in the event of power down.
Parameter
Definition
RTS On delay
Specifies the amount of time to wait after activating RTS before transmission is initiated.
The range is 0 to 65535 ms, with a default value of 0. This parameter is valid only when the
port configuration (Page 549) specifies hardware flow control. CTS is evaluated after the
RTS On delay time has expired.
This parameter is applicable for RS232 modules only.
RTS Off delay
Specifies the amount of time to wait before de-activating RTS after completion of
transmission. The range is 0 to 65535 ms, with a default value of 0. This parameter is valid
only when the port configuration (Page 549) specifies hardware flow control.
This parameter is applicable for RS232 modules only.