Can anyone tell me what the difference between these two sets of CAN Bus messages? This is from the manual of a Power Drive Unit (PDU) in the Cargo Handling System of a 747F (UPS Freight). This is the only place where the instructions are written as shown in #2. Additionally, Request #2 is the only request I can’t seem to get the intended response or result.
#1. Transmit the PDU Request Message on the CAN Bus as follows:
Arbitration ID: C5A005E
Data (0-7): 0x 00 00 10 00 00 00 00 00
#2: Transmit the PDU Request Message on the CAN Bus as follows:
Arbitration ID: C5A005E
Byte 7 through 3: 0x00
Byte 2: 0×40
Byte 1: 0x00
Byte 0: 0×40
NOTE: Sorry to anyone who cant view images
The following is a screenshot of the instructions for the initial Request for the programmed Part Number. In this step, The PDU responds as intended, with the Part Number, with one exception... the Identifier starts at "00" rather than "01".
Example Response: for PN 4345562
00 34 33 34 35 35 36 32
01 00 00 00 00 00 00 00
02 00 00 00 00 00 00 00
Next page: instructions to program the Part Number to the EEPROM, if the recalled PN is not correct.
My main question is, what would the reasoning be for writing it as:
Byte 7 through 3: 0x00
Byte 2: 0×40
Byte 1: 0x00
Byte 0: 0×40
-vs-
0x 00 00 10 00 00 00 00 00
UPDATE: CAN messages are transmitted in Little Endian Format.
Data (0-7)
implies that the first message starts with byte 0 ... please do not post pictures of text ... doing so exudes people that cannot view pictures \$\endgroup\$