MC68HC08AZ16 Datasheet, PDF (376/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

msCAN08 Controller (msCAN08)
Programmer’s model of message storage
Transmit buffer
priority registers
(TBPR)
TBPR
R
$xxbD W
RESET
BIT 7
PRIO7
U
BIT 6
PRIO5
U
BIT 5
PRIO5
U
BIT 4
PRIO4
U
BIT 3
PRIO3
U
BIT 2
PRIO2
U
BIT 1
PRIO1
U
Figure 13.Transmit buffer priority register (TBPR)
BIT 0
PRIO0
U
PRIO7 - PRIO0— Local priority
This field defines the local priority of the associated message buffer.
The local priority is used for the internal prioritization process of the
msCAN08 and is defined to be highest for the smallest binary number.
The msCAN08 implements the following internal prioritization
mechanism:
• All transmission buffers with a cleared TXE flag participate in the
prioritization right before the SOF (Start of Frame) is sent.
• The transmission buffer with the lowest local priority field wins the
prioritization.
• In case of more than one buffer having the same lowest priority the
message buffer with the lower index number wins.
CAUTION:
To ensure data integrity, no registers of the transmit buffers shall be
written while the associated TXE flag is cleared. Also, no registers of the
receive buffer shall be read while the RXF flag is cleared.
29-can
MOTOROLA
msCAN08 Controller (msCAN08)
MC68HC08AZ32
375