Routines
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933E: Test Space Key
Used by the routines at Handler_JetmanMovement, Handler_MoonRover and Handler_Pickup.
Return non-zero only on the call when SPACE (or SHIFT) goes down. SpaceKeyLatch latches the key as held until it is released.
Output
A Zero unless SPACE has just been pressed
Return non-zero when SPACE is first pressed.
TestSpaceKey 933E LD A,$7E Read from the keyboard;
Port Number Bit
0 1 2 3 4
7E SPACE FULL-STOP M N B
Shift Z X C V
9340 OUT ($FD),A
9342 IN A,($FE)
Test SPACE and clear the latch if it is up.
9344 CPL Flip the bits.
9345 AND %00000001 Keep only bit 0.
9347 JR Z,TestSpaceKey_StoreLatch If the result is zero jump to TestSpaceKey_StoreLatch.
Report a new press only if the latch was not already set.
9349 LD A,($5E5D) A=*SpaceKeyLatch.
934C AND A If A is not zero then jump to TestSpaceKey_Clear.
934D JR NZ,TestSpaceKey_Clear
934F INC A Increment A by one.
TestSpaceKey_StoreLatch 9350 LD ($5E5D),A Write A to SpaceKeyLatch.
9353 RET Return.
TestSpaceKey_Clear 9354 XOR A A=00.
9355 RET Return.
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