microchip language jal doc e0002

-- 
-- name    : e0002.jal
-- author  : Wouter van Ooijen
-- date    : 05-May-1998
-- purpose : jal example
--
-- This program shows a night-rider style LED on port B
--

-- target configuration: 16f84 with 10 Mhz Xtal
include 16f84_10

-- standard library
include jlib

-- jal has no enumerate, so use constants
const byte to_right  = 1
const byte to_left   = 0

-- determine a new direction d when x has hit a boundary,
-- shift x one step in the good direction
procedure night( byte in out x, byte in out direction ) is

   -- hit left border?
   if ( x & 0b_1000_0000 ) != 0 then
      direction = to_right
   end if

   -- hit right border?
   if ( x & 0b_0000_0001 ) != 0 then
      direction = to_left
   end if

   -- shift in current direction
   if direction == to_right then
      x = x >> 1
   else
      x = x << 1
   end if

end procedure

-- port b all pins output
port_b_direction = all_output

var byte x = 0b_0000_0001
var byte d = to_left

-- main loop
forever loop

   -- set port b
   -- for active-low LEDs remove the --
   port_b = x -- ^ 0xFF

   -- delay 200mS
   delay_100ms( 2 )

   -- shift x one step in the current direction
   night( x, d )

end loop

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