UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 515 o f 792
NXP Semiconductors UM10237
Chapter 18: LPC24XX CAN controllers CAN1/2
17.3.3 Scenario 3: Message gets overwritten indicated by Semaphore bits

This scenario is a special case in which the lost message is indicated by the existing

semaphore bits. The scenario is entered, if during a Software read of a message object

another new message gets stored by the message handler. In this case, the FullCAN

Interrupt bit gets set for a second time with the 2nd Object write.

17.3.4 Scenario 3.1: Message gets overwritten indicated by Semaphore bits and Message Lost

This scenario is a sub-case to Scenario 3 in which the lost message is indicated by the

existing semaphore bits and by Message Lost.

Fig 87. Message gets overwritten

01 11 01 1100 00
1st Object
write 2nd Object
write 2nd Object
read
1st Object read
Interrupt Service
Routine
IntPndx
semaphore
bits
look-up
table
access
MsgLostx
message
handler
access
ARM
processor
access
read
SEM
read
D2
read
D1
clear
SEM
read
SEM
write
SEM
write
D2
write
D1
write
ID,
SEM
write
SEM
write
D2
write
D1
write
ID,
SEM
read
SEM
read
D2
read
D1
clear
SEM