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For example, this filter
match(ANY, 0x00000000, 0x01FFF800)
{
}
will match all 11-bit CAN frames (for all CAN IDs in range 0x000...0x7FF we will have a match — as all such
IDs AND 0x01FFF800 expression yields 0)
The keyword
match()
is not translated into bytecode, so the comparison of the specified filters with
the messages received is very quick.
The program may contain up to 20 filters.
2. Message buffer
The subprogram has access to the message and its 29-bit CAN identifier that is stored in the buffer described
in Table 1.
Table 1. Message buffer structure
Offset
Length
in bytes
Description
0
4
29-bit identifier CAN message (LSB first)
4
1
0xFF – indicator of a single-frame NMEA 2000 message (CAN message with
29-bit identifier); 0xfe - indicator of a CAN message with an 11-bit identifier;
0x00..0xE0 in steps of 0x20 – indicator of the NMEA 2000 fast-packet message
(sequence counter); other values are reserved
5
1
Message length (1..223)
6
223
Message data
Summary of Contents for YDNB-07N
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