Routines
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24951: 'J' pressed - joystick
The address of this routine is found in the table of keypress handling routines at 60672. It is called from the main loop at 61483 when 'J' is pressed.
24951 LD A,96 Message 96: newline
24953 LD (32722),A Store this message number at 32722 so that it can be watched in the message queue
24956 CALL 30154 Queue the message urgently
24959 LD A,97 Message 97: 'JOYSTICK?'
24961 CALL 30154 Queue this message urgently
24964 CALL 30972 Wait until message 96 (newline) has left the queue (and therefore 'JOYSTICK?' is displayed)
24967 JR Z,24964
24969 CALL 60121 Wait for a keypress and collect its ASCII code in A
24972 JR Z,24969
24974 SET 5,A Convert the keypress to lower case
24976 LD HL,25019 Point HL at the keypress offset patch table at 25019
24979 LD DE,49968 Point DE at the main keypress offset table
24982 LD BC,10 There will be 10 bytes to copy
24985 CP 107 Was 'k' pressed?
24987 JR NZ,25001 Jump if not
Now HL points at the appropriate keypress offset patch table (25029 if 'i' (Int2) was pressed, or 25019 otherwise), and A holds the input device indicator (107 if 'k' (Kempston) was pressed, or 0 otherwise).
24989 PUSH HL Save the pointer to the keypress offset patch table briefly
24990 LD HL,65530 Set the input device indicator for future games at 65530
24993 LD (HL),A
24994 LD H,127 Set the input device indicator for the current game at 32762
24996 LD (HL),A
24997 POP HL Restore the address of the keypress offset patch table to HL
24998 LDIR Update the entries for keys 0-9 in the keypress offset table
25000 RET
Some key other than 'k' (Kempston) was pressed.
25001 CP 99 Was 'c' (Cursor) pressed?
25003 JR Z,25013 Jump if so
25005 CP 110 Was 'n' (None) pressed?
25007 JR Z,25013 Jump if so
25009 LD L,197 HL=25029 (keypress offset patch table for Int2)
25011 CP 105 Set the zero flag if 'i' was pressed
25013 LD A,0 0 indicates that we're not using the Kempston joystick
25015 JR Z,24989 Jump if 'i' (Int2) was pressed
25017 JR 24969 Otherwise jump back to collect another keypress
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