MA28140 datasheet(39/72 Pages) DYNEX

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MA28140

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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

: 16#301

The value of the virtual channel ID is

: 16#20

The value of the Application Process ID is

: 16#456

For the FARM-1 process, the values of PW and NW are

: 10#100 and 10#100

The Authenication MAP ID Pointer is

: 16#15

For the CPDU, the Application Process Identifier is

: 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

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

RO M

S tart Addre ss

E nd Addre ss

Frame Header octet 1 (see note 3)

000

Frame Header octet 2 (see note 3)

001

Frame Header octet 3 (see note 3)

002

FARM PW' = PW - 1 (see note 4)

003

FARM NW' = 256 - NW (see note 4)

004

Authenticated MAP ID pointer (see note 5)

005

CPDU Packet Header octet 1 and 2 (see note 6)

006

007

Free

008

0FF

MAP frequency table defined in section 5.2

100

13F

Free

140

1FF

Fixed key - Knapsack (see note 7)

200

367

Fixed key - Hashing (see note 8)

368

36F

Free

370

3FF

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