Nikon NWL860 Series, Manual

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11
Chapter 3 Interface Specification
3
4. Message
4-1. Format
4-2. Message Length
The first message byte.
This gives the total length (byte count) of the header and the message data.
4-3. Header
See “4-6. Header” in this chapter.
4-4. Message Data
See “4-7. Message Data” in this chapter.
4-5. Checksum
A 2-byte block representing the sum of the binary numbers of the header and the message data without
codes.
The upper-digit byte is sent before the lower-digit byte.
4-6. Header
4-6-1. Format
Message length 1 byte
Header 10 bytes
Message data max 244 bytes
Checksum 2 bytes
Messages consists of the following blocks.
Time
Upper device ID
Lower device ID
Upper message ID
Lower message ID
Upper block No.
Lower block No.
System byte
8 7 6 5 4 3 2 1
1
2
3
4
5
6
7
8
9
10
Device ID
Message ID
Block No.
System Byte
R
W
E
4-6-2. Device ID
Used as an identification number for each device in an SECS network.