Copy protection: SOMEPROT

       Name: SOMEPROT                                                [Show more]
       Type: Subroutine
   Category: Copy protection
    Summary: Implement the OSWORD 249 command (some copy protection)
  Deep dive: 6502 Second Processor Tube communication
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * OSWVECS calls SOMEPROT


 This routine is run when the parasite sends an OSWORD 249 command with a
 parameter block at OSSC(1 0). The parameter block is empty when the command is
 sent, and this routine copies the code between do65202 and end65C02 to the
 parameter block, just after the two size bytes.


.SOMEPROT

 LDY #2                 \ Set a counter in Y to go from 2 to 2 + protlen, so
                        \ we copy bytes from do65202 to end65C02 into byte #2
                        \ onwards in the parameter block pointed to by OSSC

.SMEPRTL

 LDA do65C02-2,Y        \ Copy the Y-th byte of do65202 to the Y+2-th byte of
 STA (OSSC),Y           \ the OSWORD parameter block

 INY                    \ Increment the loop counter

 CPY #protlen+2         \ Loop back to copy the next byte until we have copied
 BCC SMEPRTL            \ the whole of do65202 to end65C02 to the OSWORD block,
                        \ so it can be run by the parasite

 RTS                    \ Return from the subroutine