Emergency Messages; Heartbeat - Curtis 1352 Manual

3 — CANopen COMMUNICATIONS
16

EMERGENCY MESSAGES

Emergency messages are the second highest priority in CANopen and the
highest priority that a slave (like the eXm) can transmit. These messages are
sent sporadically whenever there is a change of state in the eXm's fault flags.
An Emergency Message consists of 8 data bytes.
To prevent fast-changing fault bits from flooding the bus, a minimum
time between messages can be programmed.
Data bytes 1 and 2 define the error category. The eXm will use the device-
specific category (FFXXh) per DS301. Therefore the upper byte is FFh when
a fault is present, and the lower byte is equal to the Curtis fault code. When
no faults are present and/or the last fault has just been cleared, the emergency
message will use the error code value of 0000h.
Data byte 3 is the CANopen-required error register. Curtis products define
this as 01h if there is a fault present and 00h when all faults are clear.
Data bytes 4 through 8 define the specific fault. The eXm will place the
current 16-bit hourmeter (Object 3140h) into data bytes 4 and 5, with the MSB
in byte 5. Note that bytes 6, 7, and 8 are not used by the eXm and are always
000000h. See Diagnostics (section 6) for more detail.
Emergency Message Format indicating an error:
byte 1
Curtis
FFh
Code
Error Category
Emergency Message Format indicating all error(s) cleared:
byte 1
0000h
Error Category

HEARTBEAT

The heartbeat message is a very low priority message, periodically sent by each
slave device on the bus. The heartbeat message has a single byte of data and
requires no response. Once the eXm is in the Pre-Operational state, the next
heartbeat will be issued and will continue until communication is stopped.
The heartbeat message has only one data byte. The top bit is reserved and
should be set to zero. The bottom 7 bits hold the current NMT device state as
defined previously.
byte 8
01h Object 3140h 000000h
Hourmeter
byte 8
00h Object 3140h 000000h
Hourmeter
Curtis 1352 eXm Manual,
Rev. D