MC33989PEG Freescale Semiconductor, MC33989PEG Datasheet - Page 53

• Manufacturer Part Number: MC33989PEG
• Description: SBC-HS
• Manufacturer: Freescale Semiconductor

Analysis: CAN Frame with 11 Bits of Identifier Field at 1
Analysis: CAN Frame with 11 Bits of Identifier Field at 0
FAILURE ON V2 SUPPLY, CAN BUS LINES AND TX PIN
V2LOW
TX Permanent Dominant
permanent dominant is detected if TX stays in dominant (TX low) from more than 360 μs typical. The driver is automatically re-
enabled when TX goes to a high level again. When a TX permanent dominant is detected, a bit is set into the SPI register, (bit
D2 named TXF in the CAN register). This bit is latched. In order to clear the bit, two conditions are necessary:
Analog Integrated Circuit Device Data
Freescale Semiconductor
Figure 42
Figure 43
In order to have proper operation of the CAN interface, V2 must be ON. Two case can be considered:
• V2 is connected with an external ballast: in case of a V2 over load condition, the flag V2LOW is set in to the SBC IOR
• V2 is connected to V1 (no ballast transistor used): V2 will be supplied by the V1 voltage. In case V1 is in an undervoltage
A TX permanent dominant condition is detected by the CAN interface and leads to a disable of the CAN driver. The TX
• No longer “TX permanent failure” AND
• CAN register read operation.
An interrupt can be enabled.The GFAIL flag in the MCR register will also be set.
register. This flag is set when V2 is below the 4.0 V typical. An interrupt can also be triggered upon a V2LOW event. When
V2 is low, the CAN interface cannot operate.
condition (ex V1 below the V1 under voltage reset, typ 4.6 V), the device will enter the reset mode. The V2LOW flag will
also be set. In this case, the reset pin is active, and the MCU will not send or receive any CAN messages.
17 bits are needed to wake-up the SBC.
If the minimum baud rate is used (60 KBaud), TACN = 16.7 μs*17= 284 μs
If 250 KBaud is used, TCAN = 4μs *17= 68 μs.
is the calculation for the TCAN time with only “1” in the identifier field.
is the calculation for the TCAN time with only “0” in the identifier field.
13 bits are needed to wake-up the SBC.
If the minimum baud rate is used (60 KBaud), TCAN = 16.7 μs*13= 217.1 μs
If 250 KBaud is used: TCAN = 4μs *13= 52 μs
SOF 4 dominant bits
SOF
5 recessive bits
Figure 42. CAN Frame with 11 Bits of Identifier Field at 1
Figure 43. CAN Frame with 11 Bits of Identifier Field at 0
Stuff bit
5 dominant bits
TCAN
Stuff bit
5 recessive bits
Stuff bit
2 dominant bits
Stuff bit 1 recessive bit
3 dominant bit if RTR IDE & DLC=0
SUPPLEMENTAL APPLICATION NOTES
SBC wakes up
TYPICAL APPLICATIONS
SBC wakes up
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