UMAX140610. LIN
– J1939 CAN Protocol Converter with PWM Output. Version 1
Page: 54-81
Over Temperature
N/A
Over Temperature
Shutdown
Lost Communication N/A
Received Message Timeout
(any)
When applicable, a hysteresis setpoint is provided to prevent the rapid setting and clearing of
the error flag when the measured value is right near the fault detection threshold. For the low
end, once a fault has been flagged, it will not be cleared until the measured value is greater
than or equal to the Minimum Threshold
+
“Hysteresis to Clear Fault.”
For the high end, it
will not be cleared until the measured value is less than or equal to the Maximum Threshold
–
“Hysteresis to Clear Fault.”
The minimum, maximum and hysteresis values are always
measured in the units of the fault in question.
Note: It is recommended to take in consider of another block when changing the setpoints in
Under Voltage Diagnostics block or Over Voltage. Changing for the Hysteresis in either block
will result in the change for the other block. However, disables outputs setpoint is used for their
own fault flags.
The next setpoint in these function blocks is the
“Event Generates a DTC in DM1.”
If and
only if this is set to true will the other setpoints in the function block be enabled. They are all
related to the data that is sent to the J1939 network as part of the DM1 message, Active
Diagnostic Trouble Codes.
A Diagnostic Trouble Code (DTC) is defined by the J1939 standard as a four byte value which
is a combination of:
SPN Suspect Parameter Number
(first 19 bits of the DTC, LSB first)
FMI
Failure Mode Identifier
(next 5 bits of the DTC)
CM
Conversion Method
(1 bit, always set to 0)
OC
Occurrence Count
(7 bits, number of times the fault has happened)
In addition to supporting the DM1 message, the CAN-4AOUT Controller also supports
DM2 Previously Active Diagnostic Trouble Codes
Sent only on request
DM3 Diagnostic Data Clear/Reset of Previously Active DTCs
Done only on request
DM11 Diagnostic Data Clear/Reset for Active DTCs
Done only on request
So long as even one Diagnostic function block has
“Event Generates a DTC in DM1”
set to
True, the converter will send the DM1 message every one second, regardless of whether or
not there are any active faults, as recommended by the standard. While there are no active
DTCs, the converter
will send the “No Active Faults” message. If a previously inactive DTC
becomes active, a DM1 will be sent immediately to reflect this. As soon as the last active DTC
goes inactive, it will send a DM1 indicating that there are no more active DTCs.
If there is more than one active DTC at any given time, the regular DM1 message will be sent
using a multipacket Broadcast Announce Message (BAM). If the controller receives a request
for a DM1 while this is true, it will send the multipacket message to the Requester Address
using the Transport Protocol (TP).
