UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 517 o f 792
NXP Semiconductors UM10237
Chapter 18: LPC24XX CAN controllers CAN1/2
17.3.6 Scenario 4: Clearing Message Lost bit

This scenario is a special case in which the lost message bit of an object gets set during

an overwrite of a none read message object (2nd Object write). The subsequent read out

of that object by Software (1st Object read) clears the pending Interrupt. The 3rd Object

write clears the Message Lost bit. Every “write ID, SEM” clears Message Lost bit if no

pending Interrupt of that object is set.

Fig 89. Message overwritten indicated by message lost

IntPndx
semaphore
bits
look-up
table
access
MsgLostx
message
handler
access
ARM
processor
access
write
SEM
write
D2
write
D1
write
ID,
SEM
01 11 01 11 00
1st Object
write
2nd Object
write 1st Object
read
Interrupt Service
Routine
01 11
3rd Object
write
write
SEM
write
D2
write
D1
write
ID,
SEM
write
SEM
write
D2
write
D1
write
ID,
SEM
read
SEM
read
D2
read
D1
read
SEM clear
SEM