Chapter 11 Freescale’s Scalable Controller Area Network (S12MSCANV3)
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
470
Freescale Semiconductor
11.4.5.5
MSCAN Sleep Mode
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 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.
Figure 11-46. Sleep Request / Acknowledge Cycle
NOTE
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.
If sleep mode is active, the SLPRQ and SLPAK bits are set (
). The application software must
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.
SYNC
SYNC
Bus Clock Domain
CAN Clock Domain
MSCAN
in Sleep Mode
CPU
Sleep Request
SLPRQ
Flag
SLPAK
Flag
SLPRQ
sync.
SLPAK
sync.
SLPRQ
SLPAK
Содержание MC9S12ZVHL32
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Страница 686: ...Chapter 20 ECC Generation module SRAM_ECCV1 S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 686 Freescale Semiconductor...
Страница 752: ...Chapter 22 Supply Voltage Sensor BATSV2 S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 752 Freescale Semiconductor...
Страница 774: ...Chapter 23 LIN Physical Layer S12LINPHYV2 S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 774 Freescale Semiconductor...
Страница 788: ...Appendix A MCU Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 788 Freescale Semiconductor...
Страница 794: ...Appendix B ADC Electricals S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 794 Freescale Semiconductor...
Страница 798: ...Appendix D IRC Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 798 Freescale Semiconductor...
Страница 802: ...Appendix F MSCAN Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 802 Freescale Semiconductor...
Страница 806: ...Appendix G NVM Electrical Parameters S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 806 Freescale Semiconductor...
Страница 810: ...Appendix H BATS Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 810 Freescale Semiconductor...
Страница 816: ...Appendix K OSC32K Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 816 Freescale Semiconductor...
Страница 822: ...Appendix L SPI Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 822 Freescale Semiconductor...
Страница 826: ...Appendix M LINPHY Electrical Specifications S12ZVHY S12ZVHL Family Reference Manual Rev 1 05 826 Freescale Semiconductor...
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