Lenze I/O system 1000 System Manual - Manual (Page 730)

Appendix
Serial process interfacing
Protocols
15
l
730 EDSIO1000 EN 7.0
3964(R) protocol: 3964(R) manages the data transfer of a point−to−point coupling between
the EPM−S640 or EPM−S650 I/O compound module and a communication partner.
During the data transfer, control characters are added to the user data. These enable the
communication partner to check whether the data has arrived completely and correctly.
The following control characters are evaluated:
ƒ STX (Start of Text)
ƒ DLE (Data Link Escape)
ƒ ETX (End of Text)
ƒ BCC (Block Check Character; only for 3964R)
ƒ NAK (Negative Acknowledge)
)
Note!
When a DLE is transmitted as information character, it is distinguished from
the DLE control character by being sent twice while establishing/terminating a
connection (DLE duplication). The receiver undoes the DLE duplication.
With 3964(R), the communication partner must be assigned with a lower
priority. When both communication partners place a transmit request at the
same time, the partner with lower priority will delay its transmit request.
only 3964R
STX
DLE
Telegram data
DLE
ETX
BCC
Acknowledgement time monitoring
DLE
Active partner Passive partner
Acknowledgement time monitoring
SLIO_RS002
Fig. 15−2 Sequence
You can transfer a maximum of 250 bytes per frame.
Time−out times: Acknowledgement time is monitored between STX and DLE, as well as
between BCC and DLE. Character delay time is monitored during the entire frame
reception. After the acknowledgement time has elapsed after STX, STX is retransmitted
and after 5 attempts a NAK is sent and the connection establishment is aborted. The same
happens when after a STX a NAK or any character are received. After the acknowledgement
time has elapsed after the frame (after BCC byte) or when a character unequal to DLE is
received, the connection establishment and the frame will be repeated. Here, also 5
attempts are made, afterwards a NAK is sent and the transmission is aborted.