MC68HC08AZ16 Datasheet, PDF (357/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

msCAN08 Controller (msCAN08)
The internal scheduling process takes places 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 can not 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 emitting 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 has been sent in the
meantime (ABTAK=0).
Identifier acceptance filter
A very flexible programmable generic identifier acceptance filter has
been introduced in order to reduce the CPU interrupt loading. The filter
is programmable to operate in three different modes:
• Single identifier acceptance filter to be applied to the full 29 bits of
the identifier and to the following bits of the CAN frame: RTR, IDE,
SRR. This mode implements a single filter for a full length CAN
2.0B compliant extended identifier.
• Double identifier acceptance filter to be applied to
– the 11 bits of the identifier and the RTR bit of CAN 2.0A
messages or
– the 14 most significant bits of the identifier of CAN 2.0B
messages.
• Quadruple identifier acceptance filter to be applied to the first 8
bits of the identifier. This mode implements four independent
filters for the first 8 bit of a CAN 2.0A compliant standard identifier.
MC68HC08AZ32
356
msCAN08 Controller (msCAN08)
10-can
MOTOROLA