The SwitchToFileSys (I/O processor) subroutine - Elite on the BBC Micro and NES

       Name: SwitchToFileSys                                         [Show more]
       Type: Subroutine
   Category: Utility routines
    Summary: Restore the filing system workspace to &C000 on a BBC Master
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * tube_wrch calls SwitchToFileSys


IF _BUG_FIX

.SwitchToFileSys

                        \ This routine restores the filing system workspace to
                        \ &C000 on a BBC Master, but only if we overwrote it in
                        \ SwitchToCharSet

 LDA #0                 \ Call OSBYTE with A = 0 and X = 1 to fetch bit 0 of the
 LDX #1                 \ operating system version into X
 JSR OSBYTE

 CPX #3                 \ If X =< 3 then this is not a BBC Master, so jump to
 BCC file1              \ file1 to continue drawing the character

 BIT wsstatecopy        \ If bit 7 of wsstatecopy is set then the character set
 BMI file1              \ was already present before this call, so skip the
                        \ following so we don't change that

 JSR restorews          \ Call restorews to restore the filing system workspace

.file1

 RTS                    \ Return from the subroutine

ENDIF

[X]

Configuration variable OSBYTE = &FFF4

The address for the OSBYTE routine

[X]

Label file1 is local to this routine

[X]

Configuration variable restorews = &DD65

The address for the restorews workspace routine from the loader so we can call it to ensure the MOS characterdefinitions are loaded before printing text on the BBC Master

[X]

Variable wsstatecopy in subroutine SwitchToCharSet

We store a copy of the wstate here so we know which state to switch back to after printing

Utility routines: SwitchToFileSys

[Elite-A, I/O processor]