Siemens Simatic S7-400

Receive bu󹪜er on CP
The following table describes the parameters for the CP receive bu󹪜er.
Table 5-13 Receive bu󹪜er on CP (3964(R) procedure)
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
Initial state of receive line
The table below contains a description of the initial state of the receive line for the X27 (RS 422)
interface. RS 485 operation is not possible in conjunction with the 3964(R) procedure.
Table 5-14 X27 (RS 422) interface (3964(R) procedure)
Parameter Description Value Range Default Value
Initial state of receive
line
none: This setting only makes sense with bus-ca‐
pable drivers.
none R(A) 5V / R(B) 0V
R(A) 5V/R(B) 0V: Break detection is possible with
this initial state.
R(A) 5V / R(B) 0V
(break detection)
R(A) 0V / R(B) 5V: Break detection is not possible
with this initial state.
R(A) 0V / R(B) 5V
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 67