Freescale Semiconductor, Inc.
MSCAN Controller
Programmer’s Model of Control Registers
17.12.4 Data Segment Registers (DSRn)
The eight data segment registers contain the data to be transmitted or
being received. The number of bytes to be transmitted or being received
is determined by the data length code in the corresponding DLR.
17.12.5 Transmit Buffer Priority Registers (TBPR)
BIT 7
PRIO7
–
BIT 6
PRIO6
–
BIT 5
PRIO5
–
BIT 4
PRIO4
–
BIT 3
PRIO3
–
BIT 2
PRIO2
–
BIT 1
PRIO1
–
BIT 0
PRIO0
–
TBPR(1)
$01xD
R
W
RESET
1. x is 5, 6, or 7 depending on which buffer Tx0, Tx1, or Tx2 respectively.
PRIO7 – PRIO0 — Local Priority
This field defines the local priority of the associated message buffer.
The local priority is used for the internal prioritisation process of the
msCAN12 and is defined to be highest for the smallest binary number.
The msCAN12 implements the following internal prioritisation
mechanism:
• All transmission buffers with a cleared TXE flag participate in the
prioritisation immediately before the SOF (Start of Frame) is sent.
• The transmission buffer with the lowest local priority field wins the
prioritisation.
• In cases of more than one buffer having the same lowest priority,
the message buffer with the lower index number wins.
17.13 Programmer’s Model of Control Registers
17.13.1 Overview
The programmer’s model has been laid out for maximum simplicity and
efficiency.
68HC(9)12D60 — Rev 4.0
MOTOROLA
Advance Information
MSCAN Controller
303
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