' timers1.bas
'
' This file is written for the 68HC12 by Kevin Ross (kevinro@nwlink.com)
' An article in the Seattle Robotics Society Encoder accompanies this
' file http://www.seattlerobotics.org/encoder/nov97/68hc12.html
'
' It is written in SBASIC.
' To compile this file, you need to invoke the following commands:
'
' sbasic timers.bas /cf000 /v0000 /m6812 > timers.asm
' as12 first.asm
'
include "regs12.lib"	' PORT definitions and constants

declare TicFlags
'
' Program execution starts at the Main: label, as shown here.
'
Main:

'
' This program isn't going to use the COP. It must be turned of
' right away, otherwise it might reset the chip.
'
	pokeb copctl,0
'
' Next, initialize the serial port and print a message saying we started.
'
	' Enable serial port
	poke  sc0bdh, 52	' Set for 9600 baud
	pokeb	sc0cr2,$0c	' Enable transceiver

	print "timers.bas has started"


'
' Setup channels 0 and 1 to be TOC channels.
' Setup channels 2 and 3 to be TIC channels.
'
	pokeb	tios,%00000011

'
' Set channels 0 and 1 to toggle their output pins when the compare happens
'
	pokeb	tctl2, %00000101

'
' Set the prescalar to slow the clock way way down. In fact, we want to
' have the TOC's happen every 262 milliseconds, so you can see the pins
' toggle using an LED or a logic probe. Check out the prescalar selection
' table in the 68HC812A4 Technical Summary to see how to change the rate.
'
	pokeb	tmsk2,%00110101

'
' Set the compares to trigger when TCNT == 0 and $8000
'
	poke	tc0,0
	poke	tc1,$8000

'
' Turn on the timer, disable it during background debug mode
'
	pokeb	tscr, %10100000

'
' The TOC channels are up and running. Now configure the TIC channels 2 and 3
'
' We are interested in capturing any changes in channel 2, or any rising
' edge in channel 3
'
	pokeb	tctl4,%01110000



do
	'
	' This loop is going to sit and spin, testing to see when a TIC
	' event happens. When the TIC triggers, it sets a bit in TFLG1
	' to indicate that a value is ready. To clear the flag indicating
	' the TIC has happened, we write a 1 to its position in TFLG1
	'
	TicFlags = peekb(tflg1)
	if TicFlags AND $04 <> 0
		printx "TIC2: ",peek(tc2)
		pokeb	tflg1,peekb(tflg1) OR $04
        endif
	if TicFlags AND $08 <> 0
		printx "TIC3: ",peek(tc3)
		pokeb	tflg1,peekb(tflg1) OR $08
        endif

	
loop

end