Delphi RS-232 Page 13 of, 4.4.3Received Keyword 2000 Messages, 4.4.4Format byte, Saint, 01/20/04

SAINT

Keyword 2000 to RS-232 Gateway

01/20/04

Page 13 of 20

4.4.3Received 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

4.4.4Format 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.