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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
734 of 808
NXP Semiconductors
UM10360
Chapter 34: Appendix: Cortex-M3 User Guide
See
for more information about the
IP[0]
to
IP[111]
interrupt priority array,
that provides the software view of the interrupt priorities.
Find the IPR number and byte offset for interrupt
N
as follows:
•
the corresponding IPR number,
M
, is given by
M
=
N
DIV 4
•
the byte offset of the required Priority field in this register is
N
MOD 4, where:
–
byte offset 0 refers to register bits[7:0]
–
byte offset 1 refers to register bits[15:8]
–
byte offset 2 refers to register bits[23:16]
–
byte offset 3 refers to register bits[31:24].
4.2.8 Software Trigger Interrupt Register
Write to the STIR to generate a
Software Generated Interrupt
(SGI). See the register
summary in
for the STIR attributes.
When the USERSETMPEND bit in the SCR is set to 1, unprivileged software can access
the STIR, see
Remark:
Only privileged software can enable unprivileged access to the STIR.
The bit assignments are shown in
.
4.2.9 Level-sensitive and pulse interrupts
The processor supports both level-sensitive and pulse interrupts. Pulse interrupts are also
described as edge-triggered interrupts.
A level-sensitive interrupt is held asserted until the peripheral deasserts the interrupt
signal. Typically this happens because the ISR accesses the peripheral, causing it to clear
the interrupt request. A pulse interrupt is an interrupt signal sampled synchronously on the
rising edge of the processor clock. To ensure the NVIC detects the interrupt, the
peripheral must assert the interrupt signal for at least one clock cycle, during which the
NVIC detects the pulse and latches the interrupt.
Table 623. IPR bit assignments
Bits
Name
Function
[31:24]
Priority, byte offset 3 Each priority field holds a priority value, 0-31. The lower the
value, the greater the priority of the corresponding interrupt.
The processor implements only bits[7:3] of each field, bits[2:0]
read as zero and ignore writes.
[23:16]
Priority, byte offset 2
[15:8]
Priority, byte offset 1
[7:0]
Priority, byte offset 0
Table 624. STIR bit assignments
Bits
Field
Function
[31:9]
-
Reserved.
[8:0]
INTID
Interrupt ID of the required SGI, in the range 0-111. For example, a value
of b000000011 specifies interrupt IRQ3.