MC68HC908GZ8 Datasheet, PDF (172/344 Pages) Motorola, Inc – Microcontrollers

MSCAN08 Controller (MSCAN08)
16.8 Low-Power Modes
In addition to normal mode, the MSCAN08 has three modes with reduced power
consumption: sleep, soft reset, and power down. In sleep and soft reset mode,
power consumption is reduced by stopping all clocks except those to access the
registers. In power-down mode, all clocks are stopped and no power is consumed.
The WAIT and STOP instructions put the MCU in low-power consumption stand-by
modes. Table 16-2 summarizes the combinations of MSCAN08 and CPU modes.
A particular combination of modes is entered for the given settings of the bits
SLPAK and SFTRES. For all modes, an MSCAN08 wakeup interrupt can occur
only if SLPAK = WUPIE = 1.
.
Table 16-2. MSCAN08 versus CPU Operating Modes
MSCAN08 Mode
Power Down
Sleep
Soft Reset
Normal
1. ‘X’ means don’t care.
STOP
SLPAK = X⁽¹⁾
SFTRES = X
CPU Mode
WAIT or RUN
SLPAK = 1
SFTRES = 0
SLPAK = 0
SFTRES = 1
SLPAK = 0
SFTRES = 0
16.8.1 MSCAN08 Sleep Mode
The CPU can request the MSCAN08 to enter the low-power mode by asserting
the SLPRQ bit in the module configuration register (see
Figure 16-6). The time when the MSCAN08 enters sleep mode depends on its
activity:
• If it is transmitting, it continues to transmit until there is no more message 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 or receiving, it will immediately go into sleep mode
NOTE:
The application software must avoid setting up a transmission (by clearing or more
TXE flags) and immediately request sleep mode (by setting SLPRQ). It then
depends on the exact sequence of operations whether MSCAN08 starts
transmitting or goes into sleep mode directly.
Data Sheet
172
MSCAN08 Controller (MSCAN08)
MC68HC908GZ8
Freescale Semiconductor