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⌂ ∞ ▽ Elite on the 6502

Text: MT18

[NES version, Bank 2]

       Name: MT18                                                    [Show more]
       Type: Subroutine
   Category: Text
    Summary: Print a random 1-8 letter word in Sentence Case
  Deep dive: Extended text tokens

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * JMTB calls MT18




.MT18

 JSR MT19               ; Call MT19 to capitalise the next letter (i.e. set
                        ; Sentence Case for this word only)

 JSR DORND              ; Set A and X to random numbers and reduce A to a
 AND #3                 ; random number in the range 0-3

 TAY                    ; Copy the random number into Y, so we can use Y as a
                        ; loop counter to print 1-4 words (i.e. Y+1 words)

.MT18L

 JSR DORND              ; Set A and X to random numbers and reduce A to an even
 AND #62                ; random number in the range 0-62 (as bit 0 of 62 is 0)

 TAX                    ; Copy the random number into X, so X contains the table
                        ; offset of a random extended two-letter token from 0-31
                        ; which we can now use to pick a token from the combined
                        ; tables at TKN2+2 and QQ16 (we intentionally exclude
                        ; the first token in TKN2, which contains a newline)

 LDA TKN2+2,X           ; Print the first letter of the token at TKN2+2 + X
 JSR DTS_b2

 LDA TKN2+3,X           ; Fetch the second letter of the token from TKN2+2 + X

 CMP #'?'               ; If the second letter is a question mark, skip the
 BEQ P%+5               ; following instruction (as ? indicates a single-letter
                        ; token)

 JSR DTS_b2             ; Print the second letter of the token at TKN2+2 + X

 DEY                    ; Decrement the loop counter

 BPL MT18L              ; Loop back to MT18L to print another two-letter token
                        ; until we have printed Y+1 of them

 RTS                    ; Return from the subroutine