MC68HC912B32CFU8 Freescale Semiconductor, MC68HC912B32CFU8 Datasheet - Page 253

• Manufacturer Part Number: MC68HC912B32CFU8
• Description: IC MCU 32K FLASH 8MHZ 80-QFP
• Manufacturer: Freescale Semiconductor
• Series: HC12r

Specifications of MC68HC912B32CFU8

• Core Processor: CPU12
• Core Size: 16-Bit
• Speed: 8MHz
• Connectivity: SCI, SPI
• Peripherals: POR, PWM, WDT
• Number Of I /o: 63
• Program Memory Size: 32KB (32K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 768 x 8
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 80-QFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

The time when the msCAN12 enters sleep mode depends on its activity. For instance,
During sleep mode, the SLPAK flag is set. The application software should use SLPAK as a handshake
indication for the request (SLPRQ) to go into sleep mode. When in sleep mode, the msCAN12 stops its
internal clocks. However, clocks to allow register accesses still run. If the msCAN12 is in bus-off state, it
stops counting the 128 x 11 consecutive recessive bits due to the stopped clocks. The TxCAN pin stays
in recessive state. If RXF = 1, the message can be read and RXF can be cleared. Copying RxBG into
RxFG doesn’t take place while in sleep mode. It is possible to access the transmit buffers and to clear the
TXE flags. No message abort takes place while in sleep mode.
The msCAN12 leaves sleep mode (wakeup) when one of these occurs:
After wakeup, the msCAN12 waits for 11 consecutive recessive bits to synchronize to the bus. As a
consequence, if the msCAN12 is wakened by a CAN frame, this frame is not received. The receive
message buffers (RxFG and RxBG) contain messages if they were received before sleep mode was
entered. All pending actions are executed upon wakeup: copying of RxBG into RxFG, message aborts,
and message transmissions. If the msCAN12 is still in bus-off state after sleep mode was left, it continues
counting the 128 x 11 consecutive recessive bits.
16.7.2 msCAN12 Soft-Reset Mode
In soft-reset mode, the msCAN12 is stopped. Registers can still be accessed. This mode is used to
initialize the module configuration, bit timing, and the CAN message filter. See
Module Control Register 0
When setting the SFTRES bit, the msCAN12 immediately stops all ongoing transmissions and receptions,
potentially causing the CAN protocol violations.
Freescale Semiconductor
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If it is transmitting, it continues to transmit until there are no more messages to be transmitted and
then goes into sleep mode.
If it is receiving, it waits for the end of this message and then goes into sleep mode.
If it is neither transmitting nor receiving, it immediately goes into sleep mode.
Bus activity occurs.
MCU clears the SLPRQ bit.
MCU sets SFTRES.
The application software must avoid setting up a transmission (by clearing
one or more TXE flag(s)) and immediately request sleep mode (by setting
SLPRQ). It then depends on the exact sequence of operations whether the
msCAN12 starts transmitting or goes into sleep mode directly.
The MCU cannot clear the SLPRQ bit before the msCAN12 is in sleep
mode (SLPAK = 1).
The user is responsible for ensuring that the msCAN12 is not active when
soft-reset mode is entered. The recommended procedure is to put the
msCAN12 into sleep mode before the SFTRES bit is set.
for a complete description of the soft-reset mode.
M68HC12B Family Data Sheet, Rev. 9.1
NOTE
NOTE
NOTE
16.12.1 msCAN12
Low-Power Modes
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