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base:sending_a_command_to_a_disk_drive

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base:sending_a_command_to_a_disk_drive [2015-04-17 04:33] (current)
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 +====== Sending a command to a disk drive, the easy way ======
 +
 +The easiest way of sending a command to the disk drive is by simply using the command string as filename when calling OPEN.
 +
 +BASIC code:
 +<​code>​
 +OPEN 15,​8,​15,"​I":​CLOSE 15
 +</​code>​
 +Assembler code:
 +<​code>​
 +        LDA #​cmd_end-cmd
 +        LDX #<cmd
 +        LDY #>cmd
 +        JSR $FFBD     ; call SETNAM
 +
 +        LDA #$0F      ; file number 15
 +        LDX $BA       ; last used device number
 +        BNE .skip
 +        LDX #$08      ; default to device 8
 +.skip   LDY #$0F      ; secondary address 15
 +        JSR $FFBA     ; call SETLFS
 +
 +        JSR $FFC0     ; call OPEN
 +        BCS .error ​   ; if carry set, the file could not be opened
 +.close
 +        LDA #$0F      ; filenumber 15
 +        JSR $FFC3     ; call CLOSE
 +
 +        JSR $FFCC     ; call CLRCHN
 +        RTS
 +.error
 +        ; Akkumulator contains BASIC error code
 +
 +        ; most likely errors:
 +        ; A = $05 (DEVICE NOT PRESENT)
 +
 +        ... error handling for open errors ...
 +        JMP .close ​   ; even if OPEN failed, the file has to be closed
 +
 +cmd:    .TEXT "​I" ​    ; command string
 +cmd_end:
 +</​code>​
 +
 +====== Sending a command to a disk drive, the flexible way ======
 +
 +Another way of sending a command to the disk drive is by leaving the filename string empty and send the command string afterwards. The advantage of this is that you can send several commands but only open the command channel one time.
 +
 +BASIC code:
 +<​code>​
 +OPEN 15,​8,​15:​PRINT#​15,"​I":​CLOSE 15
 +</​code>​
 +Assembler code:
 +<​code>​
 +        LDA #$00
 +        LDX #$00
 +        LDY #$00
 +        JSR $FFBD     ; call SETNAM (no filename)
 +
 +        LDA #$0F      ; file number 15
 +        LDX $BA       ; last used device number
 +        BNE .skip
 +        LDX #$08      ; default to device 8
 +.skip   LDY #$0F      ; secondary address 15
 +        JSR $FFBA     ; call SETLFS
 +
 +        JSR $FFC0     ; call OPEN
 +        BCS .error ​   ; if carry set, the file could not be opened
 +
 +        LDX #$0F      ; filenumber 15
 +        JSR $FFC9     ; call CHKOUT (file 15 now used as output)
 +
 +        LDY #$00
 +.loop   LDA cmd,y     ; get byte from command string
 +        JSR $FFD2     ; call CHROUT (send byte through command channel)
 +        INY
 +        CPY #​cmd_end-cmd
 +        BNE .loop
 +.close
 +        LDA #$0F      ; filenumber 15
 +        JSR $FFC3     ; call CLOSE
 +
 +        JSR $FFCC     ; call CLRCHN
 +        RTS
 +.error
 +        ; Akkumulator contains BASIC error code
 +
 +        ; most likely errors:
 +        ; A = $05 (DEVICE NOT PRESENT)
 +
 +        ... error handling for open errors ...
 +        JMP .close ​   ; even if OPEN failed, the file has to be closed
 +
 +cmd:    .TEXT "​I" ​    ; command string
 +        .BYTE $0D     ; carriage return, needed if more than one command is sent
 +cmd_end:
 +</​code>​
  
base/sending_a_command_to_a_disk_drive.txt ยท Last modified: 2015-04-17 04:33 (external edit)