MA28140 Datasheet, PDF (39/72 Pages) Dynex Semiconductor – Packet Telecommand Decoder

ROM
Frame Header octet 1 (see note 3)
Frame Header octet 2 (see note 3)
Frame Header octet 3 (see note 3)
FARM PW' = PW - 1 (see note 4)
FARM NW' = 256 - NW (see note 4)
Authenticated MAP ID pointer (see note 5)
CPDU Packet Header octet 1 and 2 (see note 6)
Free
MAP frequency table defined in section 5.2
Free
Fixed key - Knapsack (see note 7)
Fixed key - Hashing (see note 8)
Free
S tart Addre ss
000
001
002
003
004
005
006
008
100
140
200
368
370
E nd Addre ss
000
001
002
003
004
005
007
0FF
13F
1FF
367
36F
3FF
Note 3: These 3 octets contain all the fields of the Frame Header including reserved bits and version
bits. Bypass and Control flags (in Frame Header octet 1) form the only field that is not a fixed value:
the value of these 2 bits in ROM has no influence on the PTD operation (default value = 00).
Note 4: In order to facilitate the implementation of the FARM Sliding Window Concept in the PTD,
the values stored in the ROM are not PW and NW but:
- PW' = PW - 1
- NW' = 256 - NW
The PW' and NW' numbers can be any value between 0 and 255.
Note 5: Bits 7 and 6 are not used.
Note 6: These 2 octets contain all the field of the Packet Header including version and type bits.
Note 7: The Knapsack key mapping is given in Figure 9. Address 200 contains the least significant
octet of the first Knapsack coefficient W0. Address 201 contains octet 1 of the first Knapsack
coefficient W0, (see example below).
Note 8: The Hashing key mapping is given in Figure 9. Address 368 contains the 4 LSBs of the
Hashing key stored at the right of the memory octet in the reverse order. Address 369 contains the 8
following bits in the reverse order. Caution: if the Hashing key is read bit by bit starting from the
MSB, the memory must be filled from right to left, (see example below).
Table 6: ROM Mapping
Example
An example of ROM programming is given here for a fictitious spacecraft.
Note: In the following example 16# indicates hexadecimal, 10# indicates decimal, 2# indicates binary.
The value of the spacecraft ID is
The value of the virtual channel ID is
The value of the Application Process ID is
For the FARM-1 process, the values of PW and NW are
The Authenication MAP ID Pointer is
For the CPDU, the Application Process Identifier is
: 16#301
: 16#20
: 16#456
: 10#100 and 10#100
: 16#15
: 16#456
Frame Header octet 1 contains the following fields:
Version number
: 2#00 in accordance with ref 1
Bypass flag
: 0 or 1 (no influence): 0 for example
Control Comrnand flag : 0 or 1 (no influence): 0 for example
Reserved field A
: 2#00 in accordance with ref 1
Spacecraft ID (2 MSBs) : 2#11
The value of the ROM at address 000 is: 16#03
Frame Header octet 2 contains the following field:
Spacecraft ID (8 LSBs) : 2#00000001
The value of the ROM at address 001 is: 16#01
Frame Header octet 3 contains the following fields:
Virtual Channel ID
: 2#100000
Reserved field B
: 2#00 in accordance with ref 1
The value of the ROM at address 002 is: 16#80
MA28140
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