mc33905s Freescale Semiconductor, Inc, mc33905s Datasheet - Page 43

• Manufacturer Part Number: mc33905s
• Description: System Basis Chip Gen2 With High Speed Can And Lin Interface
• Manufacturer: Freescale Semiconductor, Inc

Conditions to set SAFE pin active low:
or at the second consecutive reset pulse (selected by bit 4,
INIT W/D register).
Analog Integrated Circuit Device Data
Freescale Semiconductor
.
Watchdog refresh issue: SAFE activated at 1st reset pulse
SAFE pin release
(SAFE high)
Failure events
Device state:
Legend:
1) bit 4 of INIT Watchdog register
2) Wake up event: CAN, LIN or I/O-1 high level (if I/O-1 wake up previously enabled)
3) SPI commands: 0xDD00 or 0xDD80 to release SAFE pin
4) Recovery: reset low condition released, Vdd low condition released, correct SPI W/D refresh
5) detection of 8 consecutive W/D failures: no correct SPI W/D refresh command occurred for duration of 8 x 256ms.
6) Dynamic behavior: 1ms reset pulse every 256ms, due to no W/D refresh SPI command, and device state transition
between RESET and NORMAL REQUEST mode, or INIT RESET and INIT modes.
7) 8 second timer for bus idle time out. I/O-1 high to low transition.
SPI (3)
Normal Request
Normal, FLASH
RESET
INIT,
W/D failure
bit 4, INIT W/D = 1 (1)
bit 4, INIT W/D = 0 (1)
Rst s/c gnd:
Rst <2.5V, t>100ms
Vdd low:
V
DD
<V
DD
_
UVTH
Figure 24. Safe Operation Flow Chart
RESET
- Reset low
- SAFE low
- Vdd ON
SAFE high
SAFE low
SAFE operation flow chart
8 consecutive W/D failure (5)
at DBG pin during
a) Evaluation of
Resistor detected
power up, or SPI
register content
- I/O-1 monitoring
b) ECU external signal
monitoring (7):
- bus idle time out
Reset: 1ms pulse
Reset: 1ms pulse
as Reset pin is set low.
clamped to a low level preventing the MCU to operate. If this
is the case, the Safe Mode is entered.
Vdd low: Vdd <
The RESET pin is monitored to verify that reset is not
Wake up (2), Vdd ON, SAFE pin remains low
detection of 2nd
consecutive W/D failure
State B2:
Rdbg=33k AND I/O-1 low
State B1: Rdbg=15k AND
Bus idle time out expired
State B3:
Rdbg=47k AND I/O-1 low
AND Bus idle time out expired
State A: Rdbg<6k AND
(Vdd low or Rst s/c gnd) failure
BEHAVIOR AT POWER UP AND POWER DOWN
State A: Rdbg<6k AND
W/D failure
failure recovery, SAFE pin remains low
SAFE low
R
ST-TH
. SAFE pin is set low at same time
RESET
FAIL SAFE OPERATION
- SAFE low
- Reset low
- Vdd OFF
- SAFE low
- Vdd ON
- Reset: 1ms
periodic pulse
- SAFE low
- Vdd ON
- Reset low
(6)
NR
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