MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
22-18
Freescale Semiconductor
CAN
x
_ESR). After the transition to the ‘error passive’ state, the TXECTR does not increment
anymore by acknowledge errors. Therefore the device never goes to the bus off state.
•
If the RXECTR increases to a value greater than 127, it is not incremented further, even if more
errors are detected while being a receiver. At the next successful message reception, the counter is
set to a value between 119 and 127 to resume to ‘error active’ state.
22.3.3.6
Error and Status Register (CANx_ESR)
CAN
x
_ESR reflects various error conditions, some general status of the device, and it is the source of two
interrupts to the CPU. The reported error conditions (bits 16–21) are those that occurred since the last time
the CPU read this register. The CPU read action clears BIT1ERR, BIT0ERR, ACKERR, CRCERR,
FRMERR, and STFERR. TXWRN, RXWRN, IDLE, TXRX, FLTCONF, BOFFINT, and ERRINT are
status bits.
Most bits in this register are read-only, except BOFFINT and ERRINT, which are interrupt flags that can
be cleared by writing 1 to them (writing 0 has no effect). See
,” for more details.
NOTE
A read clears BIT1ERR, BIT0ERR, ACKERR, CRCERR, FRMERR, and
STFERR, therefore these bits must not be read speculatively. For future
compatibility, the TLB entry covering the CAN
x
_ESR must be configured
to be guarded.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg Addr
Base + 0x001C
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
R
RXECTR
TXECTR
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg Addr
Base + 0x001C
Figure 22-7. Error Counter Register (CANx_ECR)
Summary of Contents for MPC5553
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