MC68HC908GZ8 Datasheet, PDF (192/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
MSCAN08 Controller (MSCAN08)
16.13.7 MSCAN08 Transmitter Flag Register
The abort acknowledge flags are read only. The transmitter buffer empty flags are
read and clear only. A flag can be cleared by writing a 1 to the corresponding bit
position. Writing a 0 has no effect on the flag setting. The transmitter buffer empty
flags each have an associated interrupt enable bit in the CTCR register. A hard or
soft reset will resets the register.
Address: $0506
5
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
ABTAK2 ABTAK1 ABTAK0
0
Write:
TXE2
TXE1
TXE0
Reset: 0
0
0
0
0
1
1
1
= Unimplemented
Figure 16-21. Transmitter Flag Register (CTFLG)
NOTE:
ABTAK2–ABTAK0 — Abort Acknowledge
This flag acknowledges that a message has been aborted due to a pending
abort request from the CPU. After a particular message buffer has been flagged
empty, this flag can be used by the application software to identify whether the
message has been aborted successfully or has been sent. The ABTAKx flag is
cleared implicitly whenever the corresponding TXE flag is cleared.
1 = The message has been aborted.
0 = The message has not been aborted, thus has been sent out.
TXE2–TXE0 — Transmitter Empty
This flag indicates that the associated transmit message buffer is empty, thus
not scheduled for transmission. The CPU must handshake (clear) the flag after
a message has been set up in the transmit buffer and is due for transmission.
The MSCAN08 sets the flag after the message has been sent successfully. The
flag is also set by the MSCAN08 when the transmission request was
successfully aborted due to a pending abort request (see 16.12.5 Transmit
Buffer Priority Registers). If not masked, a receive interrupt is pending while
this flag is set.
Clearing a TXEx flag also clears the corresponding ABTAKx flag (ABTAK, see
above). When a TXEx flag is set, the corresponding ABTRQx bit (ABTRQ) is
cleared. See 16.13.8 MSCAN08 Transmitter Control Register
1 = The associated message buffer is empty (not scheduled).
0 = The associated message buffer is full (loaded with a message due for
transmission).
To ensure data integrity, no registers of the transmit buffers should be written to
while the associated TXE flag is cleared.
The CTFLG register is held in the reset state when the SFTRES bit in CMCR0 is
set.
Data Sheet
192
MSCAN08 Controller (MSCAN08)
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MC68HC908GZ8
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