AN2283 Freescale Semiconductor / Motorola, AN2283 Datasheet - Page 9

• Manufacturer Part Number: AN2283
• Description: Scalable Controller Area Network (MSCAN)
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
CTFLG.TXE0 = 0
CTFLG.TXE1 = 0
CTFLG.TXE2 = 0
Transmit Buffer 0
Transmit Buffer 1
Transmit Buffer 2
Buffers FULL)
Message with
Message with
Message with
TBPR = 0x02
TBPR = 0x00
TBPR = 0x01
(All Three
STAGE 1
TX0
TX1
TX2
Motorola Scalable Controller Area Network (MSCAN) Interrupts
For example, let’s transmit these three messages at the same time:
When more than one buffer is loaded with a message, internal prioritization of
the MSCAN occurs. The TBPR (“local priority”) determines which buffer will
transmit first. The lower the TBPR the higher the priority, in the same manner
as arbitration of IDs on the bus.
In the example
message IDs. Looking at their respective TBPRs, the buffer with TBPR = 0x00
will transmit first, then the buffer with TBPR = 0x01, and lastly the buffer with
TBPR = 0x02.
Message:
Message:
Message:
Freescale Semiconductor, Inc.
transmits message)
(Transmit Buffer 1
Figure 6. Buffer Transmission Example
For More Information On This Product,
CTFLG.TXE0 = 0
CTFLG.TXE1 = 0
CTFLG.TXE2 = 0
Transmit Buffer 0
Transmit Buffer 1
Transmit Buffer 2
Message with
Message with
Message with
TBPR = 0x02
TBPR = 0x00
TBPR = 0x01
STAGE 2
TX0
TX1
TX2
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ID = 0x0230, TBPR = 0x02;
ID = 0x0016, TBPR = 0x00;
ID = 0x072F, TBPR = 0x01;
(Figure
6), all three buffers will contain the above three
transmits message)
(Transmit Buffer 2
Transmit Buffer 0
CTFLG.TXE0 = 0
Transmit Buffer 1
CTFLG.TXE1 = 1
Transmit Buffer 2
CTFLG.TXE2 = 0
Message with
Message with
TBPR = 0x02
TBPR = 0x01
STAGE 3
TX0
TX1
TX2
transmits message)
Transmission Process Overview
(Transmit Buffer 0
CTFLG.TXE0 = 0
CTFLG.TXE1 = 1
CTFLG.TXE2 = 1
Transmit Buffer 0
Transmit Buffer 1
Transmit Buffer 2
Message with
TBPR = 0x02
STAGE 4
TX0
TX1
TX2
AN2283/D
9