MC9S12G FREESCALE [Freescale Semiconductor, Inc], MC9S12G Datasheet - Page 529

• Manufacturer Part Number: MC9S12G
• Description: Ignores external trigger. Performs one conversion sequence and stops.
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

16.4.5.5
The CPU can request the MSCAN to enter this low power mode by asserting the SLPRQ bit in the
CANCTL0 register. The time when the MSCAN enters sleep mode depends on a fixed synchronization
delay and its current activity:
If sleep mode is active, the SLPRQ and SLPAK bits are set
use SLPAK as a handshake indication for the request (SLPRQ) to go into sleep mode.
When in sleep mode (SLPRQ = 1 and SLPAK = 1), the MSCAN stops its internal clocks. However, clocks
that allow register accesses from the CPU side continue to run.
If the MSCAN is in bus-off state, it stops counting the 128 occurrences of 11 consecutive recessive bits
due to the stopped clocks. TXCAN remains in a recessive state. If RXF = 1, the message can be read and
RXF can be cleared. Shifting a new message into the foreground buffer of the receiver FIFO (RxFG) does
not take place while in sleep mode.
It is possible to access the transmit buffers and to clear the associated TXE flags. No message abort takes
place while in sleep mode.
Freescale Semiconductor
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This document is valid for the S12G96 and the S12G128 device. All information related to other devices is preliminary.
If there are one or more message buffers scheduled for transmission (TXEx = 0), the MSCAN will
continue to transmit until all transmit message buffers are empty (TXEx = 1, transmitted
successfully or aborted) and then goes into sleep mode.
If the MSCAN is receiving, it continues to receive and goes into sleep mode as soon as the CAN
bus next becomes idle.
If the MSCAN is neither transmitting nor receiving, it immediately goes into sleep mode.
MSCAN Sleep Mode
The application software must avoid setting up a transmission (by clearing
one or more TXEx flag(s)) and immediately request sleep mode (by setting
SLPRQ). Whether the MSCAN starts transmitting or goes into sleep mode
directly depends on the exact sequence of operations.
Bus Clock Domain
CPU
Sleep Request
SLPAK
Flag
Figure 16-46. Sleep Request / Acknowledge Cycle
MC9S12G Family Reference Manual, Rev.1.01
SLPRQ
sync.
SLPAK
NOTE
SYNC
SYNC
Freescale’s Scalable Controller Area Network (S12MSCANV3)
CAN Clock Domain
(Figure
sync.
SLPRQ
SLPAK
16-46). The application software must
MSCAN
in Sleep Mode
SLPRQ
Flag
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