Routines
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631E: Check whether a signal has been raised
Used by the routines at 62D7 and 7DA7. On entry, A holds the event identifier, which will be one of:
A Description Flags Bit
0x00 End of lesson/playtime 7FC8 0
0x08 Teacher has arrived at the Map Room 7FC9 0
0x09 Teacher has arrived at the Reading Room 7FC9 1
0x0A Teacher has arrived at the Exam Room 7FC9 2
0x0B Teacher has arrived at the White Room 7FC9 3
0x10 Little boy no. 1 is ready to stampede 7FCA 0
0x11 Little boy no. 1 is ready to stampede again 7FCA 1
0x1A EINSTEIN or BOY WANDER is ready 7FCB 2
0x1B MR WACKER is ready 7FCB 3
0x1C ERIC has been told about EINSTEIN, BOY WANDER or ANGELFACE 7FCB 4
0x1D EINSTEIN has told MR WACKER what ERIC's up to, or ERIC has mumps 7FCB 5
The routine returns with the zero flag reset if the corresponding signal has been raised.
Input
A Event ID from a command list
631E PUSH AF Save the event identifier briefly
631F AND $F8 Keep only bits 3-7 (the byte index) and shift them into bits 0-4
6321 RRCA
6322 RRCA
6323 RRCA
6324 ADD A,$C8 Modify the LD A,(m) instruction at 6334 below so that m is 7FC8, 7FC9, 7FCA or 7FCB
6326 LD ($6335),A
6329 POP AF Restore the event identifier to A
632A AND $07 Keep only bits 0-2 (the bit index)
632C ADD A,A Modify the BIT n,A instruction at 6337 below so that n=A (0-7)
632D ADD A,A
632E ADD A,A
632F ADD A,$47
6331 LD ($6338),A
6334 LD A,($7FC8) Pick up the byte holding the signal flag for this event (the operand of this instruction is modified earlier in this routine)
6337 BIT 0,A Reset the zero flag if the signal has been raised (this instruction is modified earlier in this routine to check the appropriate bit)
6339 RET
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