Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XHY-Family Reference Manual, Rev. 1.01
354
Freescale Semiconductor
NOTE
The CANRFLG register is held in the reset state
9
when the initialization
mode is active (INITRQ = 1 and INITAK = 1). This register is writable again
as soon as the initialization mode is exited (INITRQ = 0 and INITAK = 0).
1. Read: Anytime
Write: Anytime when not in initialization mode, except RSTAT[1:0] and TSTAT[1:0] flags which are read-only; write of 1 clears
flag; write of 0 is ignored
9. The RSTAT[1:0], TSTAT[1:0] bits are not affected by initialization mode.
Table 11-11. CANRFLG Register Field Descriptions
Field
Description
7
WUPIF
Wake-Up Interrupt Flag — If the MSCAN detects CAN bus activity while in sleep mode (see
Section 11.4.5.5,
“MSCAN Sleep Mode
,”) and WUPE = 1 in CANTCTL0 (see
Section 11.3.2.1, “MSCAN Control Register 0
(CANCTL0)
”), the module will set WUPIF. If not masked, a wake-up interrupt is pending while this flag is set.
0
No wake-up activity observed while in sleep mode
1
MSCAN detected activity on the CAN bus and requested wake-up
6
CSCIF
CAN Status Change Interrupt Flag — This flag is set when the MSCAN changes its current CAN bus status
due to the actual value of the transmit error counter (TEC) and the receive error counter (REC). An additional 4-
bit (RSTAT[1:0], TSTAT[1:0]) status register, which is split into separate sections for TEC/REC, informs the
system on the actual CAN bus status (see
Section 11.3.2.6, “MSCAN Receiver Interrupt Enable Register
(CANRIER)
”). If not masked, an error interrupt is pending while this flag is set. CSCIF provides a blocking
interrupt. That guarantees that the receiver/transmitter status bits (RSTAT/TSTAT) are only updated when no
CAN status change interrupt is pending. If the TECs/RECs change their current value after the CSCIF is
asserted, which would cause an additional state change in the RSTAT/TSTAT bits, these bits keep their status
until the current CSCIF interrupt is cleared again.
0
No change in CAN bus status occurred since last interrupt
1
MSCAN changed current CAN bus status
5-4
RSTAT[1:0]
Receiver Status Bits — The values of the error counters control the actual CAN bus status of the MSCAN. As
soon as the status change interrupt flag (CSCIF) is set, these bits indicate the appropriate receiver related CAN
bus status of the MSCAN. The coding for the bits RSTAT1, RSTAT0 is:
00
RxOK: 0
≤
receive error counter
≤
96
01
RxWRN: 96
<
receive error counter
≤
127
10
RxERR: 127
<
receive error counter
11
Bus-off
(1)
: transmit error counter
>
255
3-2
TSTAT[1:0]
Transmitter Status Bits — The values of the error counters control the actual CAN bus status of the MSCAN.
As soon as the status change interrupt flag (CSCIF) is set, these bits indicate the appropriate transmitter related
CAN bus status of the MSCAN. The coding for the bits TSTAT1, TSTAT0 is:
00
TxOK: 0
≤
transmit error counter
≤
96
01
TxWRN: 96
<
transmit error counter
≤
127
10
TxERR: 127
<
transmit error counter
≤
255
11
Bus-Off: transmit error counter
>
255
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