36
FTSPARK
MessageID
Identifies the data in the DATA FIELD. Example:
commands, configuration data, real time
readings, etc. The lower the MessageID the
higher is the priority. The MessageID’s most
significant bit is reserved in order to identify a
response from a command:
MessageID (11 bits)
Bit 10
Bits 9 to 0 (10 bits)
Response (value 1)
Message code
The priorities ranges are:
•
Critical priority:
0x000 a 0x0FF
•
High priority:
0x100 a 0x1FF
•
Medium priority:
0x200 a 0x2FF
•
Low priority:
0x300 a 0x3FF
A list with all the possible MessageIDs is
presented later in this document.
10.4 DATA FIELD
In this data layout all 8 bytes of the DATA FIELD
are used as valid data (PAYLOAD). All data is
transmitted in one shot since this mode doesn’t
implement data segmentation.
DataFieldID 0x00: Standard CAN
In this data layout all 8 bytes of the DATA FIELD
are used as valid data (PAYLOAD). All data are
transmitted in one shot since this mode doesn’t
implement data segmentation.
DATA FIELD (1 to 8 bytes)
0
1
2
3
4
5
6
7
PAYLOAD
DataFieldID 0x01: Standard CAN Bridge
(bridge, gateway or converter)
In this data layout all 8 bytes of the DATA FIELD
will be forwarded by the bus converter.
The DataFieldID (0x01) is also used to identify
packets that are originated outside the CAN
bus. Bridge examples are: Standalone USB-
CAN converter, FT500’s USB-CAN bridge, etc.
DATA FIELD (1 to 8 bytes)
0
1
2
3
4
5
6
7
PAYLOAD
DataFieldID 0x02: FTCAN 2.0
This is the DataFieldID that all FuelTech’s
devices will use to communicate with each
other in the CAN bus. The data segmentation
feature is implemented in this type of data
layout. As can be seen in the diagrams below,
the segmentation feature uses the first byte of
the DATA FIELD to indicate which segment the
following bytes are associated with.
•
Single packet (all data is transmitted in
one CAN packet)
•
Segmented packet (data is transmitted in
multiples CAN packets)
Single packet
The first byte of the DATA FIELD will have the
value of 0xFF. The following 7 bytes will have
the message data (PAYLOAD).
DATA FIELD (1 to 8 bytes)
0
1
2
3
4
5
6
7
0xFF
PAYLOAD
Segmented packet
In the first byte of the DATA FIELD there will
be values ranging from 0x00 to 0xFE. The
first segment will have the 0x00 value and the
following packets will contain 0x01, 0x02 and
so on. In the first segment the 2 bytes following
the 0x00 value contain the segmentation data.
