Freescale’s Scalable Controller Area Network (S12MSCANV3)
Table 8-4. CANCTL1 Register Field Descriptions (continued)
Field
Description
2
Wake-Up Mode — If WUPE in CANCTL0 is enabled, this bit defines whether the integrated low-pass filter is
applied to protect the MSCAN from spurious wake-up (see Section 8.4.5.5, “MSCAN Sleep Mode”).
0 MSCAN wakes up on any dominant level on the CAN bus
WUPM
1 MSCAN wakes up only in case of a dominant pulse on the CAN bus that has a length of Twup
1
Sleep Mode Acknowledge — This flag indicates whether the MSCAN module has entered sleep mode (see
Section 8.4.5.5, “MSCAN Sleep Mode”). It is used as a handshake flag for the SLPRQ sleep mode request.
Sleep mode is active when SLPRQ = 1 and SLPAK = 1. Depending on the setting of WUPE, the MSCAN will
clear the flag if it detects activity on the CAN bus while in sleep mode.
SLPAK
0 Running — The MSCAN operates normally
1 Sleep mode active — The MSCAN has entered sleep mode
0
Initialization Mode Acknowledge — This flag indicates whether the MSCAN module is in initialization mode
(see Section 8.4.4.5, “MSCAN Initialization Mode”). It is used as a handshake flag for the INITRQ initialization
mode request. Initialization mode is active when INITRQ = 1 and INITAK = 1. The registers CANCTL1,
CANBTR0, CANBTR1, CANIDAC, CANIDAR0–CANIDAR7, and CANIDMR0–CANIDMR7 can be written only by
the CPU when the MSCAN is in initialization mode.
INITAK
0 Running — The MSCAN operates normally
1 Initialization mode active — The MSCAN has entered initialization mode
8.3.2.3
MSCAN Bus Timing Register 0 (CANBTR0)
The CANBTR0 register configures various CAN bus timing parameters of the MSCAN module.
Module Base + 0x0002
Access: User read/write(1)
7
6
5
4
3
2
1
0
R
SJW1
W
SJW0
BRP5
BRP4
BRP3
BRP2
BRP1
BRP0
Reset:
0
0
0
0
0
0
0
0
Figure 8-6. MSCAN Bus Timing Register 0 (CANBTR0)
1. Read: Anytime
Write: Anytime in initialization mode (INITRQ = 1 and INITAK = 1)
Table 8-5. CANBTR0 Register Field Descriptions
Field
Description
7-6
SJW[1:0]
Synchronization Jump Width — The synchronization jump width defines the maximum number of time quanta
(Tq) clock cycles a bit can be shortened or lengthened to achieve resynchronization to data transitions on the
CAN bus (see Table 8-6).
5-0
Baud Rate Prescaler — These bits determine the time quanta (Tq) clock which is used to build up the bit timing
BRP[5:0]
(see Table 8-7).
Table 8-6. Synchronization Jump Width
SJW1
SJW0
Synchronization Jump Width
0
0
1 Tq clock cycle
S12P-Family Reference Manual, Rev. 1.13
260
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