Implemented protocols in UNIGATE CL with Universal Script
Deutschmann Automation GmbH & Co. KG
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UNIGATE fieldbus gateway UNIGATE CL - ProfibusDP V. 2.3
17.6.10
10.3.1 Data structure 3964R
10.3.2 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.
10.3.3 Data communication
10.3.3.1 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.
10.3.3.2 Conflicts
10.3.3.3 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.
10.3.3.4 Retries
In the event of negative acknowledgement or timeout, a telegram transmitted by the high-priority
user is repeated twice. After this, the gateway signals communication as disturbed but still
attempts to re-establish the connection.
10.3.3.5 Initiation of data communication by the high-priority user
In the case of a negative acknowledgement or timeout, a telegram transmitted by the external
device is repeated twice before a fault is signalled.
Summary of Contents for UNIGATE CL ProfibusDP
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