X20 system modules • Analog input modules • X20AP31x1
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X20 system User's Manual 3.10
Adjusting the FlatStream
If the way messages are structured is changed, then the way data in the transmit/receive array is arranged is also
different. The following changes apply to the example given earlier.
MultiSegmentMTU
If MultiSegmentMTUs are allowed, then "open positions" in an MTU can be used. These "open positions" occur if
the last segment in a message does not fully use the entire MTU. MultiSegmentMTUs allow these bits to be used to
transmit the subsequent control bytes and segments. In the program sequence, the "nextCBPos" bit in the control
byte is set so that the receiver can correctly identify the next control byte.
Example
Three autonomous messages (7 bytes, 2 bytes and 9 bytes) are being transmitted using an MTU with a width of
7 bytes. The configuration allows transmission of MultiSegmentMTUs.
Message 1:
A1
A2
A3
A4
A5
A6
A7
B1
B2
D1
D2
D3
D4
D5
D6
D7
D8
No more data to transmit
-
-
...
-
Message 2:
Message 3:
Sequence for bus cycle 1
Sequence for bus cycle 2
Sequence for bus cycle 3
Sequence for bus cycle 4
Sequence for bus cycle 5
Sequence for bus cycle 6
D9
A2
A3
A4
C2
A1
A7
A5
A6
C1
B1
B2
C3
C4
D1
D2
D3
D4
D5
D6
C5
D7
D8
-
-
C0
-
-
-
-
-
C0
-
-
-
-
-
-
C0
-
C6
MultiSegmentMTU
-
D9
Transmit/Receive array
With 7 USINT elements according to
the configurable MTU size
Figure 153: Transmit/receive array (MultiSegmentMTUs)
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