November 19, 1993


Dear True Flight Customer,

This is a brief instruction manual for using the TrueFlight 71/84
downloader.

First, an explanation of the TrueFlight concept:

	The LIF socket can hold either a PIC16C71 or PIC16C84.  The
	device's pins are duplicated on an 18-pin plug which can take
	the place of a PIC in your target system.  So you can imagine
	a PIC plugged into your target, but with some non-intrusive
	circuitry inserted between the connection.  This extra
	circuitry can disconnect the PIC, perform some programming-
	related function, and reconnect it without any manual labor
	being done on your part.  To augment this, there is a UV
	eraser which completes the picture, by providing a means to
	re-program the device under test.  So, you have a relatively
	slow form of a ROM emulator.  It takes a little over a minute
	to erase and reprogram a '71, but only a few seconds to
	reprogram an '84.  By structuring your development cycle as
	explained below, the sixty seconds for the '71 does not have to
	be the impediment it first seems - the erasure process can
	proceed without the PC paying attention.


To hook up TrueFlight:

1)  Plug the transformer in and connect it to the jack on TrueFlight.
2)  Connect the modular cable between the DB25 and TrueFlight.
3)  Plug the DB25 into any parallel port.

4)  Plug a PIC16C71/JW or a PIC16C84 into the LIF socket, depending on what
    part you want to use.  Of course, you can program plastic '71s as well.

5)  Plug the ribbon cable between TrueFlight and a target system if you
    have one.  Note the jumper which can share 5V with the target.  You
    can't draw more than about 50ma from there.  If you have a separate
    supply on the target, keep the jumper in the 'off' position - towards
    the near edge of the board.

6)  If you are doing '71 development with a '71/JW, place the lamp module
    firmly over the LIF socket and push it down into position.

7)  Use PASMX to assemble your source code (see the associated files).

8)  Run PEPX to operate TrueFlight.  You can specify a filename from the
    command line, or load one from within.  Use the keys highlighted on
    the screen to invoke functions.  Type PEPX /H to get the command-line
    parameters list.


TrueFlight uses a special programming algorithm which extends the life
of a '71/JW device to over 2,500 cycles, instead of the usual 100 or so.
So, you can try out your '71 code many times, erase the device, and
reprogram it, without having to plug and unplug devices and fixtures.
TrueFlight can be left plugged into your target system.  The lines
requires for programming are isolated from the target and controlled by
TrueFlight during operations.  The status LED is always green in 'run'
mode and red in 'operation' mode - at which time the programming lines
are isolated from your target.


The DIP switches are as follows:

	MCLR^		- Pulls MCLR high when 'on'.

	OSC1 and OSC2	- Connects the socketed device's OSC1 and OSC2 pins
			  to the cable which connects to your target.  You
			  may need to keep these 'off' if you are using
			  crystals/resonators which are above 8 MHz, since
			  the cable presents a significant load which
			  disallows high frequencies.

	RTCC		- Connects the socketed device's RTCC pin to the
			  cable.  This should be 'on'.  This switch exists
			  for a future debugging scheme.

Note the 7-pin socket strip in the upper right corner of the board.  This
strip has the signals OSC1, OSC2, VDD, and VSS in various patterns to
allow crystals, resonators, and RC-circuit components to be plugged in.
This allows 8 MHz+ frequencies to be achieved, rather than suffering the
impeadance of the ribbon cable.


When using TrueFlight to do PIC16C71 development, we recommend that you
use the following approach, via batch file:

	1)  Program the '71 with your code in order to see it run:

		PEPX filename /P

	2)  Observe your software's behavior and make mental notes about
	    what you want to change.

	3)  Begin erasing the '71 so that when you are ready to reprogram
	    it, it may already be erased and you won't have to wait:

		PEPX /E

	4)  Go back into your source code and make your changes (this will
	    take a few minutes, presumably).

	5)  Assemble your source code:

		PASMX filename

	6)  Loop to step 1.


When using TrueFlight for the PIC16C84, all you need to do to run your
software is:

		PEPX filename /P

Whether using the '71 or '84, you can 'reset' the device by:

		PEPX /R


You are the first customers to receive this product.  There may be some
things about it which you think could be improved.  We would like to
hear from you.  We should have documentation available within a couple
weeks.  In the interrim, please call if you have any questions.

Sincerely,


Parallax, Inc.
(916) 624-8333
