Datasheet

Section 15 Controller Area Network for Tiny (TinyCAN)
Rev. 4.00 Mar. 15, 2006 Page 336 of 556
REJ09B0026-0400
15.5.4 Message Reception
Figure 15.14 shows a message reception flowchart. Figure 15.15 shows the set timing for TXPR
and TXCR during reception. A transmit request can be canceled by TXCR at any time during
reception.
Ye s
Ye s
Ye s
Ye s
No
No
No
No
Frame received
*
1
*
1
*
1
*
1
n = 0?
Receive frame ID
and Mailboxn ID + LAFM
match?
MBn in RXPR or MBn in
RFPR set to 1?
EOF received
n = 3 (n: Mailbox number)
TinyCAN is in idle state
Unread message
overwrite
Unread message
overrun
 Discard unread message
 Overwrite with receive
message
 Set MBn in UMSR to 1
 Set OVRI in TCIRR1 to 1
(when MBn in MBIMR
= 1)
 Interrupt occurred (when
OVRIM in TCIRR1 = 0)
Overwrite with unread
message
Discard receive message
Set MBn in UMSR to 1
Set OVRI in TCIRR1 to 1
(when MBn in MBIMR
= 1)
Interrupt occurred (when
OVRIM in TCIRR1 = 0)
Message reception
Note: Processing in a shaded box requires setting by software.
Write receive message
Set MBn in RXPR or
MBn in RFPR to 1
Set DFRI in TCIRR0 or
RFRI in TCIRR0 to 1
(when MBn in MBIMR
= 1)
Interrupt occurred (when
DFRIM in TCIMR0 or
RFRIM in TCIMR0 = 0)
NMC = 1?
n = n − 1
Read TCIRR
Clear MBn in UMSR to 0
DFRI in TCIRR0
set to 1?
Read MBn in RXPR = 1
OVRI in TCIRR1
set to 1?
Read MBn in UMSR = 1
Read Mailboxn
Read MBn in RXPR = 0
TinyCAN data
frame receive
operation end
MBn in UMSR
cleared to 0?
Clear MBn in RXPR to 0
RFRI in TCIRR0
set to 1?
Read MBn in RFPR = 1
Other interrupt
processing
Read Mailboxn
Read MBn in RFPR = 0
TinyCAN remote
frame receive
operation end
MBn in UMSR
cleared to 0?
Clear MBn in RFPR to 0
No
No No
NoNo
Ye s Ye s
Ye s
Ye s
Ye s
Figure 15.14 Message Reception Flowchart