MC68HC908GZ8 Datasheet, PDF (174/344 Pages) Motorola, Inc – Microcontrollers

MSCAN08 Controller (MSCAN08)
16.8.2 MSCAN08 Soft Reset Mode
In soft reset mode, the MSCAN08 is stopped. Registers can still be accessed. This
mode is used to initialize the module configuration, bit timing and the CAN
message filter. See 16.13.1 MSCAN08 Module Control Register 0 for a complete
description of the soft reset mode.
When setting the SFTRES bit, the MSCAN08 immediately stops all ongoing
transmissions and receptions, potentially causing CAN protocol violations.
NOTE:
The user is responsible to take care that the MSCAN08 is not active when soft reset
mode is entered. The recommended procedure is to bring the MSCAN08 into sleep
mode before the SFTRES bit is set.
16.8.3 MSCAN08 Power-Down Mode
The MSCAN08 is in power-down mode when the CPU is in stop mode.
When entering the power-down mode, the MSCAN08 immediately stops all
ongoing transmissions and receptions, potentially causing CAN protocol violations.
NOTE:
The user is responsible to take care that the MSCAN08 is not active when
power-down mode is entered. The recommended procedure is to bring the
MSCAN08 into sleep mode before the STOP instruction is executed.
To protect the CAN bus system from fatal consequences resulting from violations
of the above rule, the MSCAN08 drives the CAN_Tx pin into recessive state.
In power-down mode, no registers can be accessed.
MSCAN08 bus activity can wake the MCU from CPU stop/MSCAN08 power-down
mode. However, until the oscillator starts up and synchronization is achieved the
MSCAN08 will not respond to incoming data.
16.8.4 CPU Wait Mode
The MSCAN08 module remains active during CPU wait mode. The MSCAN08 will
stay synchronized to the CAN bus and generates transmit, receive, and error
interrupts to the CPU, if enabled. Any such interrupt will bring the MCU out of wait
mode.
16.8.5 Programmable Wakeup Function
The MSCAN08 can be programmed to apply a low-pass filter function to the CAN_Rx
input line while in internal sleep mode (see information on control bit WUPM in
16.13.2 MSCAN08 Module Control Register 1). This feature can be used to
protect the MSCAN08 from wakeup due to short glitches on the CAN bus lines.
Such glitches can result from electromagnetic inference within noisy environments.
Data Sheet
174
MSCAN08 Controller (MSCAN08)
MC68HC908GZ8
Freescale Semiconductor