Wait

Reads from a hardware port with a mask.

Syntax
	KeyPgDeclareDeclare KeyPgFunctionFunction Wait ( KeyPgByvalByVal port KeyPgAsAs KeyPgUshortUShort, KeyPgByvalByVal and_mask KeyPgAsAs KeyPgLongLong, 
	KeyPgByvalByVal xor_mask KeyPgAsAs KeyPgLongLong = 0 ) KeyPgAsAs KeyPgLongLong

Usage
	Wait port, and_value [, xor_value]

Parameters
	port
		Port to read.
	and_mask
		Mask value to KeyPgOpAndAnd the port value with.
	xor_mask
		Mask value to KeyPgOpXorXor the port value with.

Return Value
	0 if successful, -1 on failure.

Description
	Wait keeps reading port until the reading ANDed with and_mask and 
	optionally XORed with xor_mask gives a non-zero result.

	Example
	Wait &h3da, &h8 'Old Qbasic way of waiting for the monitor's vsync
	ScreenSync 'FreeBASIC way of accomplishing the same thing

Platform Differences
	* In the Windows and Linux versions three port numbers (&H3C7, &H3C8, 
	  &H3C9) are hooked by the graphics library when a graphics mode is in 
	  use to emulate VGA palette handling as in QB. This use is deprecated; 
	  use KeyPgPalettePalette to retrieve and set palette colors.

	* Using true port access in the Windows version requires the program to 
	  install a device driver for the present session. For that reason, 
	  Windows executables using hardware port access should be run with 
	  administrator permits each time the computer is restarted. Further 
	  runs don't require admin rights as they just use the already installed 
	  driver. The driver is only 3K in size and is embedded in the 
	  executable.

See also
	* KeyPgInpInp
	* KeyPgOutOut

   
