Document number
205065
Version
Rev. N
Issue date
2019-02-04
Sirius OBC and TCM User Manual
Page
148
of
174
Table 8.4 Software image locations
Image
Flash page number
Safe copy #1
0x00000
Safe copy #2
0x20000
Safe copy #3
0x40000
Updated copy #1
0x80000
Updated copy #2
0xA0000
Updated copy #3
0xC0000
Table 8.5 Software image header
Field
Size
Description
Image size
32 bits
The size in bytes of the software image, not
including the header, stored as a 32-bit
unsigned integer. A software image can be
264 Bytes
–
63 MB.
Checksum
32 bits
A cumulative XOR of all 32-bit words in the
image including the size, so that a cumulative
XOR of the whole image and header (including
checksum) shall evaluate to 0.
8.4.4. Limitations
If the image size is out of range for Safe image copy #1 (the final fallback image), the
bootrom will not be able to load it and the fallback option of handing execution to a damaged
software image if no other is available cannot be used.
8.5. Reset behaviour
The SoC has a clock and reset block that synchronizes the external asynchronous reset to
each clock domain. The internal soft reset, which can be commanded by software, follows
the same design philosophy i.e. is
also synchronized into the clock domain where it’s used.
8.6. General synchronize method
All signals passing clock domain crossings are either handled via asynchronous two port
FIFOs or synchronized into the other clock domain. Two flip-flops in series are used to
reduce possible metastability effects. All external signals are synchronized into its clock
domain following the above method.
8.7. Pulse command inputs
The pulse command inputs on the Sirius products can be used to force a board to reboot
from a specific image. Paired with the ability of the Sirius TCM to decode PUS-2 CPDU
telecommands without software interaction and issue pulse commands, this provides a
means to reset malfunctioning boards by direct telecommand from ground as a last resort.