MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
10-6
Freescale Semiconductor
In software vector mode, the interrupt exception handler software must read the INTC interrupt
acknowledge register (INTC_IACKR) to obtain the vector associated with the corresponding peripheral
or software interrupt request. The INTC_IACKR contains a 32-bit address containing a vector table base
address (VTBA) plus an offset to the interrupt vector (INTVEC). The address is then used to branch to the
corresponding routine for that peripheral or software interrupt source.
Figure 10-6. Software Vector Mode: Interrupt Exception Handler Address Calculation
Reading the INTC_IACKR acknowledges the INTC’s interrupt request and negates the interrupt request
to the processor. The interrupt request to the processor does not clear if a higher priority interrupt request
arrives. Even in this case, INTVEC does not update to a higher priority request until the lower priority
interrupt request is acknowledged by reading the INTC_IACKR. Reading INTC_IACKR also pushes the
PRI value in the INTC current priority register (INTC_CPR) onto the LIFO and updates PRI in the
INTC_CPR with the priority of the interrupt request. The INTC_CPR masks any peripheral or software
settable interrupt request at the same or lower priority of the current value of the PRI field in INTC_CPR
from generating an interrupt request to the processor.
The last actions of the interrupt exception handler must be the write to the end-of-interrupt register
(INTC_EOIR). Writing to the INTC_EOIR signals the end of the servicing of the interrupt request. The
INTC’s LIFO is popped into the INTC_CPR's PRI field by writing to the INTC_EOIR, and the size of a
write does not affect the operation of the write. The values and sizes written to the register neither update
the INTC_EOIR contents nor affect whether the LIFO pops. For possible future compatibility, write four
bytes of all 0s to the INTC_EOIR. The timing relationship between popping the LIFO and disabling
recognition of external input has no restriction. The writes can happen in either order.
However, disabling recognition of the external input before popping the LIFO eases the calculation of the
maximum pipe depth at the cost of postponing the servicing of the next interrupt request.
10.1.4.2
Hardware Vector Mode
In hardware vector mode, the interrupt exception handler address is specific to the peripheral or software
settable interrupt source rather than being common to all of them. No IVOR is used. The interrupt
exception handler address is calculated by hardware as shown in
. The upper half of the
interrupt vector prefix register (IVPR) is added to an offset which corresponds to the peripheral or software
interrupt source which caused the interrupt request. The offset matches the value in the Interrupt Vector
31
16
15
0
IVPR
31
28
27
16
15
0
+ IVOR4
31
28
27
16
15
0
0x0
0x0
OFFSET
OFFSET
PREFIX
0x0000
PREFIX
=
Interrupt Exception
0x0000
Handler Address
Summary of Contents for MPC5553
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