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Analog Integrated Circuit Device Data
Freescale Semiconductor
33
33889
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
TermVbat mode:
In this mode, the transmitter and receiver functions are disabled. The CANL pin is connected to VSUP through the RTL resistor
and internal pull up resistor of 12.5 kOhm. In this mode, the device monitors the bus activity and if a wake up conditions is
encountered on the CAN bus, it will wakes up the MC33889.
The device will enter into a normal request mode if low power mode was in sleep, or generates an INT. It enters into Normal
request mode if low power mode was in stop mode. If the device was in normal or stand by mode, the Rx pin will report a wake
up (feature not available on the MC33889B). See Rx pin behavior.
Bus Failure Detection
General description:
The device permanently monitors the bus lines and detects faults in normal and receive only modes. When a fault is detected,
the device automatically takes appropriate actions to minimize the system current consumption and to allow communication on
the network. Depending on the type of fault, the mode of operation, and the fault detected, the device automatically switches off
one or more of the following functions: CANL or CANH line driver, RTL or RTH termination resistors, or internal switches. These
actions are detailed in the following table.
The device permanently monitors the faults and in case of fault recovery, it automatically switches back to normal operation
and reconnects the open functions. Fault detection and recovery circuitry have internal filters and delays timing, detailed in the
AC characteristics parameters.
The failure list identification and the consequence on the device operation are described in following table. The failure
detection, and recovery principle, the transceiver state after a failure detected, timing for failure detection and recovery can be
found in the ISO11898-3 standard.
The following table is a summary of the failure identifications and of the consequences on the CAN driver and receiver when
the CAN is in Tx Rx mode.
Open wire detection operation:
Description:
The CANH and CANL open wire failures are not described in the ISO document. Open wire is only diagnostic information, as
no CAN driver or receiver state will change in case of an open wire condition.
In case one of the CAN wires are open, the communication will continue through the remaining wire. In this situation the 33889
will receive information on one wire only and the consequences are as follows:
when the bus is set in dominant:
- The differential receiver will toggle
- Only one of the single ended receivers CANH or of CANL will toggle
Bus failure
identification
Description
Consequence on CAN driver
Consequence on Rx pin
no failure
default operation: CAN H and CANL driver active,
RTH and RTL termination switched ON
default operation: Report differential
receiver output
1
CANH open wire
default operation
5
CANH shorted to GND
default operation
8, 3a
CANH shorted to VDD
(5.0 V)
CANH driver turn OFF. RTH termination switched
OFF
Rx report CANL single ended receiver
3
CANH shorted to VBAT
CANH driver turn OFF. RTH termination switched
OFF
Rx report CANL single ended receiver
2
CANL open wire
default operation
4, 7
CANL shorted to GND or
CANL shorted to CANH
CANL driver is OFF. RTL termination switched OFF Rx report CANH single ended receiver
9
CANL shorted to VDD
(5.0 V)
CANL driver is ON. RTL termination active
default operation
6
CANL shorted to VBAT
CANL driver is OFF. RTL termination switched OFF Rx report CANH single ended receiver