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Chapter 10 Freescale’s Scalable Controller Area Network (S12MSCANV3)
MC9S12XDP512 Data Sheet, Rev. 2.17
434
Freescale Semiconductor
NOTE
The CANTFLG register is held in the reset state when the initialization
modeisactive(INITRQ=1andINITAK=1).Thisregisteriswritablewhen
not in initialization mode (INITRQ = 0 and INITAK = 0).
Read: Anytime
Write: Anytime for TXEx flags when not in initialization mode; write of 1 clears flag, write of 0 is ignored
10.3.2.8
MSCAN Transmitter Interrupt Enable Register (CANTIER)
This register contains the interrupt enable bits for the transmit buffer empty interrupt flags.
7
6
5
4
3
2
1
0
R
0
0
0
0
0
TXE2
TXE1
TXE0
W
Reset:
0
0
0
0
0
1
1
1
= Unimplemented
Figure 10-10. MSCAN Transmitter Flag Register (CANTFLG)
Table 10-11. CANTFLG Register Field Descriptions
Field
Description
2:0
TXE[2:0]
Transmitter Buffer Empty
— This flag indicates that the associated transmit message buffer is empty, and thus
not scheduled for transmission. The CPU must clear the flag after a message is set up in the transmit buffer and
is due for transmission. The MSCAN sets the flag after the message is sent successfully. The flag is also set by
the MSCAN when the transmission request is successfully aborted due to a pending abort request (see
Section 10.3.2.9, “MSCAN Transmitter Message Abort Request Register (CANTARQ)
”). If not masked, a
transmit interrupt is pending while this flag is set.
Clearing a TXEx flag also clears the corresponding ABTAKx (see
Section 10.3.2.10, “MSCAN Transmitter
Message Abort Acknowledge Register (CANTAAK)
”). When a TXEx flag is set, the corresponding ABTRQx bit
is cleared (see
Section 10.3.2.9, “MSCAN Transmitter Message Abort Request Register (CANTARQ)
”).
When listen-mode is active (see
Section 10.3.2.2, “MSCAN Control Register 1 (CANCTL1)
”) the TXEx flags
cannot be cleared and no transmission is started.
Read and write accesses to the transmit buffer will be blocked, if the corresponding TXEx bit is cleared
(TXEx = 0) and the buffer is scheduled for transmission.
0 The associated message buffer is full (loaded with a message due for transmission)
1 The associated message buffer is empty (not scheduled)
7
6
5
4
3
2
1
0
R
0
0
0
0
0
TXEIE2
TXEIE1
TXEIE0
W
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 10-11. MSCAN Transmitter Interrupt Enable Register (CANTIER)