NXP Semiconductors MC9S12G - Page 580

Scalable Controller Area Network (S12MSCANV3)
MC9S12G Family Reference Manual Rev.1.27
582 NXP Semiconductors
18.3.2.6 MSCAN Receiver Interrupt Enable Register (CANRIER)
This register contains the interrupt enable bits for the interrupt flags described in the CANRFLG register.
NOTE
The CANRIER register is held in the reset state when the initialization mode
is active (INITRQ=1 and INITAK=1). This register is writable when not in
initialization mode (INITRQ=0 and INITAK=0).
The RSTATE[1:0], TSTATE[1:0] bits are not affected by initialization
mode.
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 128
10 TxERR: 128  transmit error counter 256
11 Bus-Off: 256 transmit error counter
1
OVRIF
Overrun Interrupt Flag — This flag is set when a data overrun condition occurs. If not masked, an error interrupt
is pending while this flag is set.
0 No data overrun condition
1 A data overrun detected
0
RXF
2
Receive Buffer Full Flag — RXF is set by the MSCAN when a new message is shifted in the receiver FIFO.
This flag indicates whether the shifted buffer is loaded with a correctly received message (matching identifier,
matching cyclic redundancy code (CRC) and no other errors detected). After the CPU has read that message
from the RxFG buffer in the receiver FIFO, the RXF flag must be cleared to release the buffer. A set RXF flag
prohibits the shifting of the next FIFO entry into the foreground buffer (RxFG). If not masked, a receive interrupt
is pending while this flag is set.
0 No new message available within the RxFG
1 The receiver FIFO is not empty. A new message is available in the RxFG
1
Redundant Information for the most critical CAN bus status which is “bus-off”. This only occurs if the Tx error counter exceeds
a number of 255 errors. Bus-off affects the receiver state. As soon as the transmitter leaves its bus-off state the receiver state
skips to RxOK too. Refer also to TSTAT[1:0] coding in this register.
2
To ensure data integrity, do not read the receive buffer registers while the RXF flag is cleared. For MCUs with dual CPUs,
reading the receive buffer registers while the RXF flag is cleared may result in a CPU fault condition.
Module Base + 0x0005 Access: User read/write
1
1
Read: Anytime
Write: Anytime when not in initialization mode
76543210
R
WUPIE CSCIE RSTATE1 RSTATE0 TSTATE1 TSTATE0 OVRIE RXFIE
W
Reset:00000000
Figure 18-9. MSCAN Receiver Interrupt Enable Register (CANRIER)
Table 18-11. CANRFLG Register Field Descriptions (continued)
Field Description