Interrupts

Introduction and Overview

The new IOMD or ARM 7500 chips used under RISC OS 3.5 and 3.6 use new device numbers (see Device numbers). These are:

0 Printer interrupt from controller

1 Unused

2 Floppy disc Index

3 VSync Pulse

4 Power on reset - this should never appear in normal use

5 IOC Timer 0

6 IOC Timer 1

7 FIQ Downgrade - reserved for the use of the current owner of FIQ

8 Expansion card FIQ Downgrade - this should normally be masked off

9 IDE hard disc interrupt

10 Serial port interrupt from controller - also mapped to FIQ device 4

11 Network card interrupt

12 Floppy disc interrupt from controller

13 Expansion card interrupt

14 Keyboard serial transmit register empty

15 Keyboard serial receive register full

16 DMA channel 0

17 DMA channel 1

18 DMA channel 2

19 DMA channel 3

20 DMA sound channel 0

21 DMA sound channel 1

22 ARM 7500 mouse port receive register full

23 ARM 7500 mouse port transmit register empty

24 ARM 7500 joystick A-to-D completion

25 ARM 7500 event 1

26 ARM 7500 event 2

Note that device numbers 22 - 26 are available with an ARM 7500, but not with an IOMD.