Datasheet

Section 15 Controller Area Network for Tiny (TinyCAN)
Rev. 4.00 Mar. 15, 2006 Page 327 of 556
REJ09B0026-0400
15.5.3 Message Transmission
Message Transmission Request: Figure 15.6 shows a transmission flowchart.
DART = 1?
or
MBn in TXCR = 1?
Ye s
Ye s
Ye s
Ye s
No
No
No
No
Update data in Mailbox n
(n = 1 to 3)
Write 1 to MBn in TXPR
Internal arbitration determination
Transmission start
Error detected or
CAN bus arbitration lost?
MBn in TXACK = 1?
Transmission completed
• Clear MBn in TXPR to 0
• Set MBn in TXACK to 1
• Mailbox empty interrupt (EMPI)
occurred (when EMPIM = 0)
Clear EMPI in TCIRR1 to 0
Read TCIRR
Read 0 from MBn in TXACK
Clear MBn in TXACK to 0
Read 1 from MBn in ABACK
Clear MBn in ABACK to 0
Read 0 from MBn in ABACK
Ye s
No
Transmission pending?
MBn in TXCR = 1?
Ye s
No
Other interrupt processing
Note: Processing in a shaded box requires setting by software.
Transmission canceled
• Clear MBn in TXPR to 0
• Clear MBn in TXCR to 0 (when MBn in TXCR = 1)
• Set MBn in ABACK to 1
• Mailbox empty interrupt (EMPI) occurred
(when EMPIM = 0)
EMPI in TCIRR1 = 1?
Clear EMPI in TCIRR1 to 0
TinyCAN in normal mode
(MBn in MBCR = 0)
Transmit processing for
Mailbox n completed
Figure 15.6 Transmission Request Flowchart