Keyboard: scan_xin

       Name: scan_xin                                                [Show more]
       Type: Subroutine
   Category: Keyboard
    Summary: Implement the scan_xin command (scan the keyboard for a specific
             key press)
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * tube_table calls scan_xin


 This routine is run when the parasite sends a scan_xin command. It scans the
 keyboard to see if the specified key is being pressed and returns the result
 to the parasite as follows. If the key is being pressed, the result contains
 the original key number in but with bit 7 set (i.e. key number +128). If the
 key is not being pressed, the result contains the unchanged key number.


.scan_xin

 JSR tube_get           \ Get the parameter from the parasite for the command:
 TAX                    \
                        \   =scan_xin(key_number)
                        \
                        \ and store it as follows:
                        \
                        \   * X = the internal key number to scan for

 JSR DKS4               \ Scan the keyboard to see if the key in X is currently
                        \ being pressed, returning the result in A and X

 JMP tube_put           \ Send A back to the parasite and return from the
                        \ subroutine using a tail call