UMAX090600 Version 1
Preliminary Documentation – May be Subject to Change
18-48
1.8.
CAN Transmit Function Block
Figure 6: CAN Transmit Function Block
The CAN Transmit function block is used to send any output from another function block (i.e. input,
status or feedback signals) to the J1939 network.
Normally, to disable a transmit message, the
“Transmit Repetition Rate”
is set to zero. However,
should message share its Parameter Group Number (PGN) with another message, this is not
necessarily true. In the case where multiple messages share the same
“Transmit PGN”
, the
repetition rate selected in the message with the LOWEST number will be used for ALL the messages
that use that PGN.
By default, all messages are sent on Proprietary B PGNs as broadcast messages. The default
settings do ‘bundle’ multiple messages onto a PGN, as outlined in Section 3. If all of the data is not
necessary, disable the entire message by setting the lowest channel using that PGN to zero. If some
of the data is not necessary, simply change the PGN of the superfluous channel(s) to an unused
value in the Proprietary B range.
Since the defaults are PropB messages, the
“Transmit Message Priority”
is always initialized to 6
(low priority) and the
“Destination Address (for PDU1)”
setpoint is not used. This setpoint is only
valid when a PDU1 PGN has been select, and it can be set either to the Global Address (0xFF) for
broadcasts, or sent to a specific address as setup by the user.
