XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 275

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

16.7.2 msCAN12 Soft-Reset Mode
16.7.3 msCAN12 Power-Down Mode
16.7.4 Programmable Wakeup Function
M68HC12B Family — Rev. 8.0
MOTOROLA
NOTE:
NOTE:
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.
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
description of the soft-reset mode.
When setting the SFTRES bit, the msCAN12 immediately stops all ongoing
transmissions and receptions, potentially causing the CAN protocol violations.
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.
The msCAN12 is in power-down mode when either of these occurs:
When entering power-down mode, the msCAN12 immediately stops all on-going
transmissions and receptions, potentially causing CAN protocol violations.
The user should be careful that the msCAN12 is not active when power-down
mode is entered. The recommended procedure is to put the msCAN12 into sleep
mode before the STOP instruction — or the WAI instruction, if CSWAI is set — is
executed.
To protect the CAN bus system from fatal consequences of violations to this rule,
the msCAN12 will drive the TxCAN pin into recessive state.
In power-down mode, no registers can be accessed.
The msCAN12 can be programmed to apply a low-pass filter function to the
RxCAN input line while in sleep mode. See control bit WUPM in the module control
register,
protect the msCAN12 from wakeup due to short glitches on the CAN bus lines.
Such glitches can result from electromagnetic interference within noisy
environments.
•
•
CPU is in stop mode.
CPU is in wait mode and the CSWAI bit is set. See
Module Control Register 0
Register1.
16.12.2 msCAN12 Module Control
16.12.1 msCAN12 Module Control Register 0
msCAN12 Controller
and
16.12.2 msCAN12 Module Control
Register1. This feature can be used to
16.12.1 msCAN12
msCAN12 Controller
Low-Power Modes
for a complete
Data Sheet
275