Routines
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B759: Read Keyboard Port
Used by the routines at HandleAttackingTool, PlayMusic_WaitKey, GameOver, WaitForKeyPress, GameMenu, ReadInterface2Joystick, ReadCursorJoystick, ReadKeyboard and PauseGame.
Reads some rows of the keyboard. The row selector is also written to port FD (with the selector as the high byte of the address), which does nothing on a 48K Spectrum and is not part of any sound; the keyboard is read with the same selector straight afterwards.
Input
A Row selector (a bit which is reset selects the row)
Output
A Keys pressed, in bits 0 to 4 (a bit is set when a key is pressed)
F Zero flag set if no key is pressed
Write the selector, then read the keys.
ReadKeyboardPort B759 OUT ($FD),A Write the row selector to port FD.
B75B IN A,($FE) Read the rows of the keyboard.
B75D CPL Invert the bits, so that a bit is set for a key which is pressed.
B75E AND %00011111 Keep only bits 0 to 4.
B760 RET Return.
View the equivalent code in;
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