MC68HC908AZ60 Datasheet, PDF (349/480 Pages) Motorola, Inc – HCMOS Microcontroller Unit

MSCAN Controller (MSCAN08)
Low Power Modes
Table 2. MSCAN08 vs CPU operating modes
MSCAN
Mode
Power Down
CPU Mode
STOP
SLPAK = X⁽¹⁾
SFTRES = X
WAIT or RUN
Sleep
SLPAK = 1
SFTRES = 0
Soft Reset
SLPAK = 0
SFTRES = 1
Normal
SLPAK = 0
SFTRES = 0
1. ‘X’ means don’t care.
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 6). The time when the MSCAN08 enters Sleep mode depends on
its activity:
• if it is transmitting, it continues to transmit untl 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 sequesnce of operations
whether MSCAN08 starts transmitting or goes into Sleep mode directly.
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 MSCAN08 stops its
internal clocks. However, clocks to allow register accesses still run. If the
MSCAN08 is in buss-off state, it stops counting the 128*11 consecutive
recessive bits due to the stopped clocks. The TxCAN pin stays in
17-mscan
MOTOROLA
MSCAN Controller (MSCAN08)
MC68HC908AZ60 — Rev 2.0
347