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87C196CB SUPPLEMENT
7-32
7.7 DETERMINING THE CAN CONTROLLER’S INTERRUPT STATUS
A successful reception or transmission or a change in the status register can cause the CAN con-
troller to generate an interrupt request. The INT_PEND1 register (see Table 7-2 on page 7-3) in-
dicates whether a CAN interrupt request is pending. The CAN interrupt pending register (Figure
7-19) indicates the source of the request (either the status register or a specific message object).
Your interrupt service routine should read the CAN_INT register to ensure that no additional in-
terrupts are pending before executing the return instruction.
If a status change generated the interrupt (CAN_INT = 01H), software can read the CAN status
register (Figure 7-20) to determine the source of the interrupt request.
CAN_INT
read-only (87C196CB)
Address:
Reset State:
1E5FH
00H
The CAN interrupt pending (CAN_INT) register indicates the source of the highest priority pending
interrupt. If a status change generated the interrupt request, software can read the status register
(CAN_STAT) to determine whether the interrupt request was caused by an abnormal error rate, a
successful reception, a successful transmission, or a new error. If an individual message object
generated the interrupt request, software can read the associated message object control 0 register
(CAN_MSG
x
CON0). The INT_PND bit-pair will be set, indicating that a receive or transmit interrupt
request is pending.
7 0
87C196CB
Pending Interrupt
Bit
Number
Function
7:0 Pending Interrupt
This field indicates the source of the highest priority pending interrupt.
Value Pending Interrupt Priority (15 is highest; 0 is lowest)
00H none —
01H status register 15
02H message object 15 14
03H message object 1 13
04H message object 2 12
05H message object 3 11
06H message object 4 10
07H message object 5 9
08H message object 6 8
09H message object 7 7
0AH message object 8 6
0BH message object 9 5
0CH message object 10 4
0DH message object 11 3
0EH message object 12 2
0FH message object 13 1
10H message object 14 0
Figure 7-19. CAN Interrupt Pending (CAN_INT) Register