P912XDP512F0MPVR datasheet(434/1348 Pages) FREESCALE

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Chapter 10 Freescale’s Scalable Controller Area Network (S12MSCANV3)

MC9S12XDP512 Data Sheet, Rev. 2.21

434

Freescale Semiconductor

NOTE

The CANTFLG 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).

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.

76543210

TXE2

TXE1

TXE0

Reset:

00000111

= 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)

76543210

00000

TXEIE2

TXEIE1

TXEIE0

Reset:

00000000

= Unimplemented

Figure 10-11. MSCAN Transmitter Interrupt Enable Register (CANTIER)

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