EXOS 2.1 Constants

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4. EXOS Variable Numbers

Below is a list of all the EXOS variables supported by the EXOS kernel and built in devices. More details of their functions can be found in the appropriate device or kernel specification.

0 - IRQ_ENABLE_STATE

      b0 - set to enable sound IRQ.
      b2 - set to enable 1Hz IRQ.
      b4 - set to enable video IRQ.
      b6 - set to enable external IRQ.
b1,3,5,7 - must be zero               

1 - FLAG_SOFT_IRQ

This is the byte set non­zero by a device to cause a software interrupt. It could also be set by the user to cause a software interrupt directly. This variable is also available at a fixed address given in an earlier section.

2 - CODE_SOFT_IRQ

This is the copy of the flag set by the device and is the variable that should be inspected by a software interrupt service routine to determine the reason for the interrupt.

3 - DEF_TYPE

Type of default device:

0 => non file handling device (eg. TAPE).

1 => file handling device (eg. DISK).

4 - DEF_CHAN

Default channel number. This channel number will be used whenever a channel call is made with channel number 255.

5 - TIMER

1Hz down counter. Will cause a software interrupt when it reaches zero and will then stop.

6 - LOCK_KEY

Current keyboard lock status.

7 - CLICK_KEY

=0 : Key click enabled.

8 - STOP_IRQ

=0 : STOP key causes soft IRQ.

¬0 : STOP key returns code.

9 - KEY_IRQ

=0 : Any key press causes soft IRQ, as well as returning a code.

10 - RATE_KEY

Keyboard auto­repeat rate in 1/50 seconds.

11 - DELAY_KEY

Delay until auto­repeat starts (=0 : no auto­repeat).

12 - TAPE_SND

=0 : Tape sound feedthrough enabled.

13 - WAIT_SND

=0 : Sound driver waits when queue full.

¬0 : Returns .SQFUL error when queue full.

14 - MUTE_SND

=0 : Internal speaker active.

¬0 : Internal speaker disabled.

15 - BUF_SND

Sound envelope storage size in phases.

16 - BAUD_SER

Defines serial baud rate.

17 - FORM_SER

Defines serial word format.

18 - ADDR_NET

Network address of this machine.

19 - NET_IRQ

=0 : Data received on network will cause a software interrupt.

20 - CHAN_NET

Channel number of network block received.

21 - MACH_NET

Source machine number of network block.

22 - MODE_VID : Video Mode,

23 - COLR_VID : Colour Mode,

24 - X_SIZ_VID: X page size,

25 - Y_SIZ_VID: Y page size

These variables select the characteristics of a video page page when it is opened.

26 - ST_FLAG

=0 : Status line is displayed.

27 - BORD_VID

Border colour of screen.

28 - BIAS_VID

Colour bias for palette colours 8 ··· 16.

29 - VID_EDIT

Channel number of video page for editor.

30 - KEY_EDIT

Channel number of keyboard for editor.

31 - BUF_EDIT

Size of edit buffer (in 256 byte pages).

32 - FLG_EDIT

Flags to control reading from editor.

33 - SP_TAPE

Non­zero to force slow tape saving.

34 - PROTECT

Non­zero to make cassette write out protected file.

35 - LV_TAPE

Controls tape output level

36 - REM1

37 - REM2

State of cassette remote controls, zero is off, non­zero is on.

38 - SPRITE

Controls external sprite colour priority.

39 - RANDOM_IRQ

Incremented on every interrupt. Can be used as a source of random numbers provided it is only accessed infrequently.

Next Chapter: Software Interrupt Codes.