msCAN12 Controller
M68HC12B Family Data Sheet, Rev. 9.1
262
Freescale Semiconductor
PRIO7–PRIO0— Local Priority
This field defines the local priority of the associated message buffer. The local priority is used for the
internal prioritization process of the msCAN12 and is defined to be highest for the smallest binary
number. The msCAN12 implements this internal prioritization mechanism:
–
All transmission buffers with a cleared TXE flag participate in the prioritization right before the
start of frame (SOF) is sent.
–
The transmission buffer with the lowest local priority field wins the prioritization.
–
In case of more than one buffer having the same lowest priority, the message buffer with the
lowest index number wins.
16.12 Programmer’s Model of Control Registers
The programmer’s model has been laid out for maximum simplicity and efficiency.
16.12.1 msCAN12 Module Control Register 0
CSWAI — CAN Stops in Wait Mode Bit
0 = The module is not affected during wait mode.
1 = The module ceases to be clocked during wait mode.
SYNCH — Synchronized Status Bit
This bit indicates whether the msCAN12 is synchronized to the CAN bus and as such can participate
in the communication process.
0 = msCAN12 is not synchronized to the CAN bus.
1 = msCAN12 is synchronized to the CAN bus.
TLNKEN — Timer Enable Flag
This flag is used to establish a link between the msCAN12 and the on-chip timer. See
16.8 Timer Link
.
0 = Port is connected to the timer input.
1 = msCAN12 timer signal output is connected to the timer input.
SLPAK — Sleep Mode Acknowledge Flag
This flag indicates whether the msCAN12 is in module internal sleep mode. It shall be used as a
handshake for the sleep mode request. See
16.7.1 msCAN12 Sleep Mode
.
0 = Wakeup – The msCAN12 is not in sleep mode.
1 = Sleep – The msCAN12 is in sleep mode.
SLPRQ — Sleep Request, Go To Sleep Mode Flag
This flag requests the msCAN12 to go into an internal power-saving mode (see
16.7.1 msCAN12
Sleep Mode
).
0 = Wakeup – The msCAN12 will function normally.
1 = Sleep request – The msCAN12 will go into sleep mode.
Address: $0100
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
CSWAI
SYNCH
TLNKEN
SLPAK
SLPRQ
SFTRES
Write:
Reset:
0
0
1
0
0
0
0
1
= Unimplemented
Figure 16-16. msCAN12 Module Control Register 0 (CMCR0)