Implemented protocols in UNIGATE® MB
Deutschmann Automation GmbH & Co. KG
20
UNIGATE
®
fieldbus gateway UNIGATE
®
MB - EtherCAT
®
V. 1.4
17.7.17
8.3 Protocol: 3964(R)
The 3964 protocol is used to transfer data between two serial devices. One partner must be a
high-priority partner and the other must be a low-priority partner in order to resolve initialisation
conflicts.
8.3.1
Data structure 3964R
8.3.2
Protocol definitions
STX
Data
DLE
ETX
BCC
The telegram format is as follows:
•
The received net data is forwarded (transparently) in both directions unchanged.
Attention:
The DLE-doubling is excluded from it; that means one DLE (10H) on the bus-side is
sent on the RS-side twice. A double DLE on the RS-side is only sent once to the bus-master.
•
Data blocking is not scheduled.
•
The net data length is restricted to 236 bytes per telegram.
•
Communication always runs between high-priority and low-priority communication partners.
8.3.3
Data communication
8.3.3.1
Initiation of data communication by the low-priority user
If the low-priority user also receives an STX in response to a transmitted STX, it interrupts its
transmit request, reverts to Receive mode and acknowledges the received STX with DLE.
A DLE in the data string is duplicated and included in the checksum. The BCC is computed from
XORing all characters.
8.3.3.2
Conflicts
8.3.3.3
Timeout times
The timeout times are preset by the definition of the 3964R protocol and cannot be overwritten !!!
tq = acknowledgement timeout time (2 s).
The acknowledgement timeout time is started after transmission of control character STX. If no
positive acknowledgement arrives within the acknowledgement timeout time, the job is repeated
(max. 2 x). If it has not been possible to complete the job positively after two repetitions, the
high-priority device nevertheless attempts to establish contact with the low-priority partner by
transmitting STX (cycle corresponds to tq).
tz = character timeout time ( 200 ms)
If the 3964 R driver receives data, it monitors arrival of the individual characters within period tz.
If no character is received within the timeout time, the protocol terminates transfer. No
acknowledgement is sent to the coupling partner.
Summary of Contents for UNIGATE MB EtherCAT
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