The BRKBK subroutine - Elite on the BBC Micro

       Name: BRKBK                                                   [Show more]
       Type: Subroutine
   Category: Save and load
    Summary: Set the standard BRKV handler for the game
    Context: See this subroutine in context in the source code
 Variations: See code variations for this subroutine in the different versions
 References: This subroutine is called as follows:
             * S% calls BRKBK


.BRKBK

 LDA #LO(BRBR)          \ Set BRKV to point to the BRBR routine
 STA BRKV
 LDA #HI(BRBR)
 STA BRKV+1

 LDA #LO(CHPR)          \ Set WRCHV to point to the CHPR routine
 STA WRCHV
 LDA #HI(CHPR)
 STA WRCHV+1

 JSR SAVEZP             \ Call SAVEZP to backup the top part of zero page

 JSR STARTUP            \ Call STARTUP to set various vectors, interrupts and
                        \ timers

 JMP SRESET             \ Call SRESET to reset the sound buffers and return from
                        \ the subroutine using a tail call

IF _SNG47

 CLI                    \ These instructions are never reached and have no
 RTI                    \ effect

ENDIF

[X]

Subroutine BRBR (category: Utility routines)

The standard BRKV handler for the game

[X]
Configuration variable: BRKV = &0202
The break vector that we intercept to enable us to handle and display system errors

[X]

Subroutine CHPR (category: Text)

Print a character at the text cursor by poking into screen memory

[X]

Subroutine SAVEZP (category: Utility routines)

Save zero page (&0090 to &00FF) into the buffer at &3000

[X]

Subroutine SRESET (category: Sound)

Reset the sound buffer and turn off all sound channels

[X]

Subroutine STARTUP (category: Loader)

Set the various vectors, interrupts and timers

[X]
Configuration variable: WRCHV = &020E
The WRCHV vector that we intercept to implement our own custom OSWRCH commands for communicating over the Tube