Document number
205065
Version
Rev. N
Issue date
2019-02-04
Sirius OBC and TCM User Manual
Page
122
of
174
Direct mode
Continuous/circular
mode
Free
pointer
Write
pointer
4 Gbytes
Unused space
Used space
Figure 7.5 Illustration of partition modes and the free/write pointers
7.9.1.2. Partition segment size
The segment size is only applicable for downloading and for partitions of type PUS (see
below). The mass memory supports segment sizes of 16, 32, and 64 kbyte.
7.9.1.3. Partition type
Partitions can be of two types, PUS (see[RD4]) and raw.
Partitions of
type PUS
requires that each segment will begin with a PUS packet and unless
auto-padding is used, it is up to the software writing into the mass memory to maintain this
segmentation. There are no limitations on the number of PUS packets that can be contained
in one segment, but if the written data doesn't fit exactly into the segment size it must be
padded up to the segment boundary. Padding can be achieved either with a PUS idle packet
(which also will be transferred to ground) or with a bit pattern of 0xF5, allowing padding of as
little as one byte. During a download operation when the padding bit pattern is discovered,
download will skip to the next segment (if available).
