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9337: Check whether ENTER or the fire button is being pressed
Used by the routine at 92DC. Returns with the zero flag reset if ENTER or the fire button on the joystick is being pressed.
9337 LD A,($8459) Pick up the Kempston joystick indicator from 8459
933A OR A Is the joystick connected?
933B JR Z,$9342 Jump if not
933D IN A,($1F) Collect input from the joystick
933F BIT 4,A Is the fire button being pressed?
9341 RET NZ Return (with the zero flag reset) if so
9342 LD BC,$BFFE Read keys H-J-K-L-ENTER
9345 IN A,(C)
9347 AND $01 Keep only bit 0 of the result (ENTER)
9349 CP $01 Reset the zero flag if ENTER is being pressed
934B RET
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