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SBASIC Manual - Page 35

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     SBasic User's Manual     SBasic Version 2.7             Page 35
     Printed:  December 5, 1999

          +-------------+
          |              | = LROLL()    |              | = RROLL()
          xxxxxxxxxxxxxxxx              xxxxxxxxxxxxxxxx



     The PEEK function returns the 16-bit value stored in a specific
     address.  This is the usual function for reading 16-bit I/O ports.

     Example:

          a = peek($1000)          ' get 16-bit value from address $1000

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

     Example:
          const porta = $1000      ' define address of port A
          a = peek(porta)          ' get 16-bit value at port A


     The PEEKB function returns the 8-bit value stored in a specific
     address.  This is the usual function for reading 8-bit I/O ports.

     Example:
          
          a = peekb($1020)         ' get 8-bit value from address $1020

     Recall that the = (assignment) operator writes a 16-bit value to a
     variable.  In the case of the PEEKB function, the top eight bits of
     the variable will always be written as 0.  Thus, reading a value of
     $45 in the above example results in storing $0045 in variable A.

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

     Example:

          const portb = $1020      ' define address of port B
          a = peekb(portb)         ' get 8-bit value at port B


     The POKE statement writes a 16-bit value to a specific address.  This
     is the usual statement for writing data to 16-bit I/O ports.

     Example:

          poke $1000, a            ' write value in A to address $1000

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