Siemens Simatic S7-400 - Page 61

Data 󹪞ow control
The table below contains descriptions of the parameters for data 󹪞ow control. Data 󹪞ow control
is only possible when "Full Duplex (RS 422) Four-Wire Mode Point to Point" is set.
Table 5-7 Data 󹪞ow control (ASCII driver)
Parameter Description Value Range Default Value
Data 󹪞ow control De󹪝nes which data 󹪞ow control procedure
is used.
• None
• XON/XOFF
none
XON character
(1)
Code for XON character
• with 7 data bits:
0 to 7FH (Hex)
(2)
• with 8 data bits:
0 to FFH (Hex)
(2)
11 (DC1)
XOFF character
(1)
Code for XOFF character
• with 7 data bits:
0 to 7FH (Hex)
(2)
• with 8 data bits:
0 to FFH (Hex)
(2)
13 (DC3)
Waiting for XON after
XOFF (wait time for
CTS=ON)
(1)
Period of time for which the CP 440 should
wait for the XON code or for CTS="ON" of
the communication partner when send‐
ing.
• 20 ms to 65530 ms
in 10 ms increments
20000 ms
(1)
Only for data 󹪞ow control with XON/XOFF.
(2)
Depending on whether you set 7 or 8 data bits for the character frame.
Receive bu󹪜er on CP
The following table describes the parameters for the CP receive bu󹪜er.
Table 5-8 Receive bu󹪜er on CP (ASCII Driver)
Parameter Description Value Range Default Value
Delete CP receive bu󹪜er
at startup
During power up or during transition of the CPU from
STOP to RUN the CP receive bu󹪜er is deleted.
• Yes
• No
No
Bu󹪜ered receive mes‐
sage frames
You can specify the number of receive message frames
to be bu󹪜ered in the CP receive bu󹪜er or to use the whole
bu󹪜er. If you use the whole bu󹪜er of 2000 bytes, the
number of bu󹪜ered receive message frames depends
only on the length of the frames.
If you specify "1" here and deactivate the following pa‐
rameter "prevent overwrite" and cyclically read the re‐
ceived data from the user program, a current message
frame will always be sent to the CPU.
• 1 to 10
• Use whole bu󹪜er
Use whole bu󹪜er
Prevent overwrite You can use this parameter to prevent data in the receive
bu󹪜er being overwritten when the bu󹪜er is full.
• Yes
• No
Yes
Con󹪝guring and Parameter Assignment the CP 440
5.4 Con󹪝guration data
Point-to-point connection CP 440 Installation and Parameter Assignment
Equipment Manual, 03/2022, A5E00057742-AE 61