Datasheet

MSCAN Controller (MSCAN08)
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
276 Freescale Semiconductor
.
23.8.1 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 23-6). 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.
Figure 23-6. Sleep Request/Acknowledge Cycle
Table 23-2. MSCAN08 versus CPU Operating Modes
MSCAN Mode
CPU Mode
STOP WAIT or RUN
Power Down
SLPAK = X
(1)
SFTRES = X
1. ‘X’ means don’t care.
Sleep
SLPAK = 1
SFTRES = 0
Soft Reset
SLPAK = 0
SFTRES = 1
Normal
SLPAK = 0
SFTRES = 0
MSCAN08 Running
SLPRQ = 0
SLPAK = 0
Sleep Request
SLPRQ = 1
SLPAK = 0
MSCAN08 Sleeping
SLPRQ = 1
SLPAK = 1
MCU
MSCAN08
MCU
or MSCAN08