Routines
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63171: Read Control Input
Used by the routine at Main_Game_Loop.
Reads the active control input for the current control mode stored in *50431. Scales the mode index to a word offset, loads the handler address from the table at Control_Handler_Table, pushes Read_Control_Input_Return as the return address, and jumps to the handler. Each handler reads one or more hardware ports and returns the direction and fire bits in A. The common landing pad at Read_Control_Input_Return masks the result to five bits and stores it in B and C.
Output
A Active-low direction and fire bits in the lower five bits
B Copy of A; the 63486 row result in split keyboard mode
C Copy of A; the 61438 row result in split keyboard mode
Read_Control_Input 63171 LD HL,63197 Point to the handler table at Control_Handler_Table and zero D.
63174 LD D,0
63176 LD A,(50431) Scale *50431 to a zero-based word table offset in E.
63179 DEC A
63180 ADD A,A
63181 LD E,A
63182 ADD HL,DE Load the handler address from the table.
63183 LD E,(HL)
63184 INC HL
63185 LD D,(HL)
63186 EX DE,HL
63187 LD DE,63192 Push the return address.
63190 PUSH DE
63191 JP (HL) Dispatch to the control handler.
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