MC68HC08AZ60ACFU MOTOROLA [Motorola, Inc], MC68HC08AZ60ACFU Datasheet - Page 352

• Manufacturer Part Number: MC68HC08AZ60ACFU
• Description: Microcontrollers
• Manufacturer: MOTOROLA [Motorola, Inc]

MSCAN08 Controller (MSCAN08)
21.6 Identifier Acceptance Filter
Advance Information
352
The internal scheduling process takes place whenever the MSCAN08
arbitrates for the bus. This is also the case after the occurrence of a
transmission error.
When a high priority message is scheduled by the application software,
it may become necessary to abort a lower priority message being set up
in one of the three transmit buffers. As messages that are already under
transmission cannot be aborted, the user has to request the abort by
setting the corresponding abort request flag (ABTRQ) in the
transmission control register (CTCR). The MSCAN08 will then grant the
request, if possible, by setting the corresponding abort request
acknowledge (ABTAK) and the TXE flag in order to release the buffer
and by generating a transmit interrupt. The transmit interrupt handler
software can tell from the setting of the ABTAK flag whether the
message was actually aborted (ABTAK = 1) or sent (ABTAK = 0).
The Identifier Acceptance Registers (CIDAR0-3) define the acceptance
patterns of the standard or extended identifier (ID10-ID0 or ID28-ID0).
Any of these bits can be marked ‘don’t care’ in the Identifier Mask
Registers (CIDMR0-3).
A filter hit is indicated to the application on software by a set RXF
(Receive Buffer Full Flag, see
(CRFLG)
Register (see
page 389). These Identifier Hit Flags (IDHIT1-0) clearly identify the filter
section that caused the acceptance. They simplify the application
software’s task to identify the cause of the receiver interrupt. In case that
more than one hit occurs (two or more filters match) the lower hit has
priority.
A very flexible programmable generic identifier acceptance filter has
been introduced to reduce the CPU interrupt loading. The filter is
programmable to operate in four different modes:
MSCAN08 Controller (MSCAN08)
on page 383) and two bits in the Identifier Acceptance Control
MSCAN08 Identifier Acceptance Control Register
MSCAN08 Receiver Flag Register
MC68HC08AZ60A — Rev 0.0
MOTOROLA
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