System Control Module

9.2.1.3Interrupt Controller Mask Register (ICMR)

The interrupt controller mask register (ICMR) contains one mask bit per pending interrupt bit (32 total). The mask bits control whether a pending interrupt bit will generate a processor interrupt (IRQ or FIQ). When a pending interrupt becomes active, it is sent to the CPU only if its corresponding ICMR mask bit is set to a one. Note that the mask bits are ignored when the SA-1100 is in idle mode. While in idle, if any interrupt source makes a request, the corresponding pending bit is set and the interrupt automatically becomes active, regardless of the state of its mask bit.

Mask bits serve two purposes. First, they allow periodic software polling of interruptible sources while preventing them from actually causing an interrupt. Second, they allow the interrupt handler routine to prevent interrupts of lower priority from occurring while still maintaining a list of pending interrupts that may have occurred previously (or during the servicing of another interrupt). The ICMR is not initialized at reset; a question mark indicates that the values are unknown at reset.

The following table shows the bit locations corresponding to the 32 separate interrupt mask bits.

Bit

31

30

29

28

27

26

25

24

23

22

21

20

19

18

17

16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

R/W

IM31

IM30

IM29

IM28

IM27

IM26

IM25

IM24

IM23

IM22

IM21

IM20

IM19

IM18

IM17

IM16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reset

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

Bit

R/W

Reset

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

IM15

IM14

IM13

IM12

IM11

IM10

IM9

IM8

IM7

IM6

IM5

IM4

IM3

IM2

IM1

IM0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

?

Bit

Name

Description

 

 

 

{n}

IM{n}

Interrupt mask n (where n = 0 through 31).

 

 

0 – Pending interrupt is masked from becoming active (interrupts not sent to CPU, Power

 

 

Manager).

 

 

1 – Pending interrupt is allowed to become active (interrupt sent to CPU, Power

 

 

Manager).

 

 

Note: IM bits are ignored during idle mode.

 

 

 

9-14

SA-1100 Developer’s Manual

Page 84
Image 84
Intel SA-1100 manual Interrupt Controller Mask Register Icmr, IMn Interrupt mask n where n = 0 through