The CBYTE() function converts its argument to an unsigned 8-bit byte value.

DECLARE FUNCTION CBYTE AS BYTE (arg AS INT) SHARED STATIC INLINE
DECLARE FUNCTION CBYTE AS BYTE (arg AS WORD) OVERLOAD SHARED STATIC INLINE
DECLARE FUNCTION CBYTE AS BYTE (arg AS LONG) OVERLOAD SHARED STATIC INLINE
DECLARE FUNCTION CBYTE AS BYTE (arg AS FLOAT) OVERLOAD SHARED STATIC INLINE

If the argument is an INT, WORD or LONG then the function will truncate the number to 8 bits, keeping the least significant byte and discarding the rest. If the argument is a FLOAT then it will be rounded, converted to fixed point, and then truncated to 8 bits.

PRINT CBYTE(-1) : REM integer to byte, outputs 255
PRINT CBYTE(65535) : REM word to byte, outputs 255
PRINT CBYTE(100.4) : REM float to byte, outputs 100