build versions

	0.1 time keeping, rotate through three outputs, one minute each,
	0.2 rate detection, vary the time for each output,
	0.3 connected output detection, test the outputs for pull-ups.
	1.0 release

chip selection

	12c509jw prototype
	12c508-04/p production

fabrication

	veroboard
	header pins
	plastic box
	screw terminals

version 0.1

	use flasher/flasher.asm as code outline

	time keeping, rotate through three outputs, one minute each,

	use counters in RAM and a main loop at the reset vector so as
	to avoid problems due to spontaneous device reset.

	use a RAM mask of output pins to reduce reset time, and force
	them and TRIS as part of the main loop.

	use internal oscillator to free GP4 and GP5.

	rotate between solenoids, running them for one minute at a
	time.

	port allocations 

		GP0, solenoid zero, resistor to ground
		GP1, solenoid one, resistor to ground
		GP2, solenoid two, resistor to ground
		GP3, not connected
		GP4, not connected
		GP5, not connected

version 0.2 

	rate detection, vary the time for each output,

	input pin tied to ground, supply, or specific output pin to
	select run time per solenoid, up to seven options,

		connected to Vss, always low, one minute,
		connected to Vdd, always high, five minutes,
		connected to GP0, ten minutes, 
		connected to GP1, fifteen minutes, 
		connected to GP2, thirty minutes, 
		connected to GP4, one hour,
		connected to GP5, two hours.

	port allocations 

		GP0, solenoid zero, resistor to ground
		GP1, solenoid one, resistor to ground
		GP2, solenoid two, resistor to ground
		GP3, select run time, connected to GP2
		GP4, not connected
		GP5, not connected

version 0.3 

	connected output detection, test the outputs for pull-ups.

	detect if the output is tied through resistor to ground or to
	supply, and if to ground then the output is to be used.

	port allocations 

		GP0, solenoid zero, resistor to ground
		GP1, solenoid one, resistor to ground
		GP2, solenoid two, resistor to ground
		GP3, select run time, connected to GP2
		GP4, resistor to supply
		GP5, resistor to supply

design review during coding

	For 0.1, pass 50Hz AC into GP5 as external clock source?
	Configuration bit _XT_OSC

$Id: design.txt,v 1.1 2001/10/16 10:43:10 james Exp james $