Document number
205065
Version
Rev. N
Issue date
2019-02-04
Sirius OBC and TCM User Manual
Page
123
of
174
Packet 1
Packet 1
Packet 2
Packet 3
Packet 4
Packet 5
Packet 2
Packet 3
Packet 4
Idle packet
Packet 1
Packet 2
Packet 3
Packet 4
Packet 5
Packet 6
Padding
Segment 1
No padding required
Segment 2
Padding with idle packet
Segment 3
Padding with bit pattern
Segment boundary
Figure 7.6 Illustration of packet placement inside segments with different padding (marked in grey)
Partitions of
type raw
are currently not supported for download, but imposes no other
limitations.
7.9.1.4. Automatic padding
Continuous and circular partitions can be configured with automatic padding of segments,
which automatically pads data written to the partition with a 0xF5 bit pattern, such that
written data never overlaps a segment boundary, and is fit for download.
Adjusted write
Written Pad
Free space
Written data
Before write
Segment
boundary
Segment 1
Segment 2
Result of write
Free space
Requested write
Figure 7-7 Illustration of auto-padding of a requested write.
No examination or validation of data contents are done in the padding process, and if a write
command with data containing multiple packets is received, it will be padded as if it was a
single large packet.
Auto-padding will never split the data in a received write command, and thus writing with
data that is larger than a segment is not supported.
If writing packets to an auto-padded partition, each write should contain data that starts at
the beginning of a packet and ends at the end of a packet, in order to ensure that it is
possible to download the data correctly.
Reads from an auto-padded partition will return padding and data as it was written to the
partition in the auto-padding procedure.