X20 system modules • Other functions • X20CM4810
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X20 system User's Manual 3.10
FlatStream mode register
In the input direction, the transmit array is generated automatically. This register offers two options to the user
that allow an incoming data stream to have a more compact arrangement. Once enabled, the program code for
evaluation must be adapted accordingly.
Information:
All B&R modules that offer FlatStream mode support the options "Large segments" and "MultiSeg-
mentMTUs" in the output direction. Compact transmission only needs to be explicitly allowed in the
input direction.
Bit structure:
Bit
Name
Information
0
MultiSegmentMTU
0
Not permitted (default; can't be configured)
1
Large segments
0
Not permitted (default; can't be configured)
2-7
Reserved
Default:
By default, both options relating to compact transmission in the input direction are disabled.
1. The module only forms segments that are at least one byte smaller than the enabled MTU. Each sequence
begins with a control byte so that the data stream is clearly structured and relatively easy to evaluate.
2. Since a FlatStream message can be of any length, the last segment of the message frequently doesn't fill up
all of the MTU's space. By default, the remaining bytes during this type of transfer cycle are not used.
Bus cycle 1
Control byte with MessageEndBit = 0
Bus cycle 2
Bus cycle 3
-
-
-
ME1
C
ME1
C
ME0
C
ME1
C
Control byte with MessageEndBit = 1
Segment 1
Segment 2
Segment 3
Message 1
Message 2
ME0
C
Figure 729: Message arrangement in the MTU (default)
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