--
-- file      : shiftIn.jal
-- author    : special [k]
-- date      : 28-JAN-2004
-- purpose   : Shift in data
-- pins      : Defined below
--
-- Copyright (C) 2004 special [k]
--
-- This library is free software; you can redistribute it and/or
-- modify it under the terms of the GNU Library General Public
-- License as published by the Free Software Foundation; either
-- version 2 of the License, or (at your option) any later version.
--
-- This library is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-- Library General Public License for more details.
-- 
-- You should have received a copy of the GNU Library General Public
-- License along with this library; if not, write to the
-- Free Software Foundation, Inc., 59 Temple Place - Suite 330,
-- Boston, MA  02111-1307, USA.
--

-- --------------------------------------------------------------------------------
-- shiftIn(extInClock, theInMode)
-- If extInClock = high and theInMode = 0 then shift in theData MSB first; sample bits during clock pulse
-- If extInClock = high and theInMode = 1 then shift in theData LSB first; sample bits during clock pulse
-- If extInClock = low and theInMode = 0 then shift in theData MSB first; sample bits before clock pulse
-- If extInClock = low and theInMode = 1 then shift in theData LSB first; sample bits before clock pulse
-- If extInClock = low and theInMode = 2 then shift in theData MSB first; sample bits during clock pulse
-- If extInClock = low and theInMode = 3 then shift in theData LSB first; sample bits during clock pulse
-- If extInClock = low and theInMode = 4 then shift in theData MSB first; sample bits after clock pulse
-- If extInClock = low and theInMode = 5 then shift in theData LSB first; sample bits after clock pulse
-- --------------------------------------------------------------------------------
procedure _shiftInDelay is
--	delay_100mS(5)
end procedure

var volatile bit shiftInClk is gp5
var volatile bit shiftInClkDir is gp5_direction
var volatile bit shiftInData is gp3
var volatile bit shiftInDataDir is gp3_direction

function shiftIn( bit in extInClock, byte in theInMode) return byte is
	shiftInData = low
	shiftInDataDir = input

	var byte theInData = 0
   	if extInClock then
		shiftInClk = low
		shiftInClkDir = input
		if theInMode == 0 then
			-- MSB first
			var bit dataBit at theInData : 0
			for 8 loop
				while ! shiftInClk loop
				end loop
				theInData = theInData << 1
				dataBit = shiftInData
				while shiftInClk loop
				end loop
			end loop
		elsif theInMode == 1 then
			-- LSB first
			var bit dataBit at theInData : 7
			for 8 loop
				while ! shiftInClk loop
				end loop
				theInData = theInData >> 1
				dataBit = shiftInData
				while shiftInClk loop
				end loop
			end loop
		end if
	else
		shiftInClk = low
		shiftInClkDir = output
		if theInMode == 0 then
			-- MSB first; sample bits before clock pulse
			var bit dataBit at theInData : 0
			shiftInClk = low
			for 8 loop
				theInData = theInData << 1
				dataBit = shiftInData
				_shiftInDelay
				shiftInClk = high
				_shiftInDelay 
				shiftInClk = low
			end loop
		elsif theInMode == 1 then
			-- LSB first; sample bits before clock pulse
			var bit dataBit at theInData : 7
			shiftInClk = low
			for 8 loop
				theInData = theInData >> 1
				dataBit = shiftInData
				_shiftInDelay
				shiftInClk = high
				_shiftInDelay 
				shiftInClk = low
			end loop
		elsif theInMode == 2 then
			-- MSB first; sample bits during clock pulse
			var bit dataBit at theInData : 0
			shiftInClk = low
			for 8 loop
				theInData = theInData << 1
				_shiftInDelay
				shiftInClk = high
				dataBit = shiftInData
				_shiftInDelay 
				shiftInClk = low
			end loop
		elsif theInMode == 3 then
			-- LSB first; sample bits during clock pulse
			var bit dataBit at theInData : 7
			shiftInClk = low
			for 8 loop
				theInData = theInData >> 1
				_shiftInDelay
				shiftInClk = high
				dataBit = shiftInData
				_shiftInDelay 
				shiftInClk = low
			end loop
		elsif theInMode == 4 then
			-- MSB first; sample bits after clock pulse
			var bit dataBit at theInData : 0
			shiftInClk = low
			for 8 loop
				_shiftInDelay
				shiftInClk = high
				_shiftInDelay 
				shiftInClk = low
				theInData = theInData << 1
				dataBit = shiftInData
			end loop
		elsif theInMode == 5 then
			-- LSB first; sample bits after clock pulse
			var bit dataBit at theInData : 7
			shiftInClk = low
			for 8 loop
				_shiftInDelay
				shiftInClk = high
				_shiftInDelay 
				shiftInClk = low
				theInData = theInData >> 1
				dataBit = shiftInData
			end loop
		end if
	end if
	return theInData
end function
-- --------------------------------------------------------------------------------