Siemens SIMATIC CP 440 Manual page 79

Protocol
The following table describes the 3964(R) protocol.
Table 5-10 3964(R) Protocol
Parameter
3964 Default Values
Without Block Check
3964(R) No Default Values
With Block Check
3964 No Default Values
Without Block Check
3964(R) No Default Values
With Block Check
Point-to-point connection CP 440 Installation and Parameter Assignment
A5E00057742-02
Configuring and Parameterizing the CP 440
Description
The protocol parameters are set to default values.
If the CP440 detects the string DLE ETX, it stops
receiving and sends DLE to the communication
partner if the block was received without errors, or
NAK if there were errors.
The protocol parameters are set to default values.
If the CP440 detects the string DLE ETX BCC, it
stops receiving and compares the received block
check character (BCC) with the longitudinal parity
calculated internally. If the BCC is correct and no
other receive errors have occurred, the CP440
sends the DLE code to the communication partner
(in the event of an error, the NAK code is sent).
The protocol parameters are programmable.
If the CP440 detects the string DLE ETX, it stops
receiving and sends DLE to the communication
partner if the block was received without errors, or
NAK if there were errors.
The protocol parameters are programmable.
If the CP440 detects the string DLE ETX BCC, it
stops receiving and compares the received block
check character (BCC) with the longitudinal parity
calculated internally. If the BCC is correct and no
other receive errors have occurred, the CP440
sends the DLE code to the communication partner
(in the event of an error, the NAK code is sent).
Default Value
3964(R) Default
Values With
Block Check:
Char. delay time
= 220 ms
Ack. delay time Ack delay time
= 2000 ms
Setup
attempts = 6
Transmission
attempts = 6
5-15