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     SBasic User's Manual     SBasic Version 2.7             Page 36
     Printed:  December 5, 1999

     You can make your use of POKE easier to understand if you combine it
     with named constants defined with the CONST statement.

     Example:

          const porta = $1000      ' define address of port A
          poke porta, a            ' write value in A to port A


     The POKEB statement writes a 8-bit value to a specific address.  This
     is the usual statement for writing data to 8-bit I/O ports.

     Example:

          pokeb $1000, a      ' write low 8 bits in A to addr $1000

     Note the difference in syntax between the PEEKB function and the POKEB
     statement; PEEKB uses parentheses around the address argument, while
     POKEB does not use parentheses.

     You can make your use of POKEB easier to understand if you combine it
     with named constants defined with the CONST statement.

     Example:

          const porta = $1000      ' define address of port A
          pokeb porta, a           ' write low 8 bits in A to port A


     The WAITWHILE and WAITUNTIL statements provide high-speed testing
     loops, for use with 8-bit I/O ports.  You can use these single
     statements to replace larger, less efficient wait-loops built from the
     PEEKB function.

     The WAITWHILE statement loops while the contents of an 8-bit port,
     ANDed with an 8-bit mask, yields a non-zero result.  The WAITUNTIL
     statement does the opposite; it loops UNTIL the contents of an 8-bit
     value, ANDed with an 8-bit mask, yields a non-zero result.

     Example:

          waitwhile $1000, $40     ' wait while bit 6 of $1000 is high

     This statement repeatedly reads the 8-bit value at address $1000 and
     ANDs that value with $40, for so long as the result is not zero.  When
     the result equals zero, the loop terminates.

     Example:

          waituntil j, n           ' wait until mask of value at j is not 0