AN1077 データシートの表示（PDF） - STMicroelectronics
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AN1077 Datasheet PDF : 14 Pages
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OVERVIEW OF ENHANCED CAN CONTROLLERS FOR ST7 AND ST9 MCUS
Figure 1. Figure 1: bxCAN Block Diagram
Master Control
Master Status
Transmit Control
Transmit Status
Transmit Priority
Receive FIFO
Interrupt Enable
Page Select
Error Status
Error Int. Enable
Tx Error Counter
Rx Error Counter
Diagnostic
Bit Timing
Filter Mode
Filter Config.
Tx Mailboxes
Mailbox 2
Mailbox 1
Mailbox 0
Transmission
Scheduler
Receive FIFO 0
2
1
Mailbox 0
Receive FIFO 1
2
1
Mailbox 0
Filter
Acceptance Filters
0
1
2
3
4
5
6
7
CAN 2.0B Active Core
3.3 TRANSMISSION HANDLING
Three transmit mailboxes are provided to the application to set-up messages for transmission.
Three mailboxes reduce software queuing and allow deterministic transmission. The Trans-
mission Scheduler decides which mailbox has to be transmitted first according to the priority
rules. Transmit Priority Rules BxCAN provides two modes for the transmit priority:
s In identifier mode when more than one transmit mailbox are pending, the identifier of the
message stored in the mailbox gives the transmission order. The message with the lowest
identifier value has the highest priority according to the arbitration of the CAN protocol.
s In FIFO mode the priority order is given by the transmit request order. This mode is well
suited for segmented transmission.
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