The Definitive Guide to the ARM Cortex-M3

Appendix D: NVIC Registers Quick Reference

Table D.1: Interrupt Controller Type Register (0xE000E004)

Bits

Name

Type

Reset Value

Description

4:0

INTLINESNUM

R

-

Number of interrupt inputs in step of 32:

0 = 1 to 32

1 = 33 to 64

Table D.2: SYSTICK Control and Status Register (0xE000E010)

Bits

Name

Type

Reset Value

Descriptions

16

COUNTFLAG

R

0

Read as 1 if counter reach 0 since last time this register is read. Clear to 0 automatically when read or when current counter value is cleared.

2

CLKSOURCE

R/W

0

0 = external reference clock (STCLK)

1 = use core clock

1

TICKINT

R/W

0

1 = Enable SYSTICK interrupt generation when SYSTICK timer reaches 0

0 = Do not generate interrupt

0

ENABLE

R/W

0

SYSTICK timer enable

Table D.3: SYSTICK Reload Value Register (0xE000E014)

Bits

Name

Type

Reset Value

Descriptions

23:0

RELOAD

R/W

0

Reload value when timer reaches 0

Table D.4: SYSTICK Current Value Register (0xE000E018)

Bits

Name

Type

Reset Value

Descriptions

23:0

CURRENT

R/Wc

0

Read to return current value of the timer

Write to clear counter to 0; clearing of current value should also clear COUNTFLAG in SYSTICK Control and Status register

Table D.5: SYSTICK Calibration Value Register (0xE000E01C)

Bits

Name

Type

Reset Value

Description

31

NOREF

R

-

1 = No external reference clock (STCLK not available)

0 = External reference clock available

30

SKEW

R

-

1 = calibration value is not exactly 10 ms

0 = calibration value is accurate

23:0

TENMS

R/W

0

Calibration value for...

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