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SAINT
Keyword 2000 to RS-
232 Gateway
01/20/04 Page 12 of 20
4.4.2 Transmitted Keyword 2000 Messages
The following is the format for sending a Keyword 2000 message:
Header SID (Service Identification Byte) N Data Bytes
28h Byte 2 Bytes 3 (2+N)
The above information is used to form the following message which is sent onto the Keyword 2000 bus (with
Length Byte not included in the Format Byte):
Format Target Source Length SID N Data Bytes Checksum
Byte 1 Byte2 Byte 3 Byte 4 Byte 5 Bytes 6 (5+N) Byte (6+N)
The above information is used to form the following message which is sent onto the Keyword 2000 bus (with
Length Byte included in the Format Byte):
Format Target Source SID N Data Bytes Checksum
Byte 1 Byte2 Byte 3 Byte 4 Bytes 5 (6+N) Byte (5+N)
Also, the SAINT will check to see if the bus is “initialized” and if necessary will send the Fast initialization
sequence (transmit Wakeup Pattern of 25msec logic low and 25msec logic high followed by a Start
Communications request message 81 11 F1 81 04). Refer to the “Keyword Protocol 2000 Data Link Layer
Recommended Practice” section 5.1.5.3 for more information.
Currently, only the Fast Initialization sequence is supported. Future initialization sequences will be added as
needed.