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SAINT
Keyword 2000 to RS-
232 Gateway
01/20/04 Page 13 of 20
4.4.3 Received Keyword 2000 Messages
The following are the 4 possible formats of a received Keyword 2000 message with time stamp information:
Header Format SID N Data Bytes Checksum Time MSB Time LSB
29h Byte2 Byte 3 Bytes 4 - (3+N) Byte 4+N Byte 5+N Byte 6+N
Header Format Length SID N Data Bytes Checksum Time MSB Time LSB
29h Byte2 Byte 3 Byte 4 Bytes 5 - (4+N) Byte 5+N Byte 6+N Byte 7+N
Header Format Target Source SID N Data Bytes Checksum Time MSB Time LSB
29h Byte2 Byte 3 Byte 4 Byte 5 Bytes 6 - (5+N) Byte 6+N Byte 7+N Byte 8+N
Header Format Target Source Length SID N Data Bytes Checksum Time MSB Time LSB
29h Byte2 Byte 3 Byte 4 Byte 5 Byte 6 Bytes 7 - (6+N) Byte 7+N Byte 8+N Byte 9+N
4.4.4 Format byte
The format byte contains a 6-bit length information and a 2-bit address mode information.
Bit 7 Bit 6 Address Information
0 0 no address informatio
0 1 exception mode (CARB)
1 0 with address information, physical addressing
1 1 with address information, functional addressing
Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Length
X X X X X X Define length of message from the Data to Checksum (not
included) bytes. A message length of 1 to 63 bytes is possible. If bits 5-0 are zero then the additional length byte
is included. Refer to the “Keyword Protocol 2000 Data Link Layer Recommended Practice” section 4.1.1 for more
information.