Subject:                        Time:
10:47 AM
                            16F872 vs 16F84
12/27/00
                                                             Date:
A few points in favor of the 16F872:

1)  It's cheaper:  16872 for $3.50 vs $4.70 for the 16F84A from:
             http://www.phanderson.com/ordering.html
2)  More features:  see data sheet at:
http://www.microchip.com/10/lit/pline/picmicro/families/16f87x/datasheet/3
0221\index.htm
3)  Easy programmer:  see adapter cable that may work with your present
16F84 programmer at:
     http://piclist.com/techref/piclist/cheapic/index.htm
4) Or even simpler programmer:  lately I've been using my version of
QANDD.  QANDD can be found at:
  http://ubasics.com/adam/pic/archive.shtml
  download pic894v05.zip

Here is my version.  Try to imagine this in your mind:

*  If you can't find a 28 pin 'skinny' dip socket, try to find two 14 pin
DIP sockets that will fit end to end
*  4.5 volts, 3 AA batteries in holder + connected to Vdd, (pin 20) and -
connected to Vss, (pin 19).  ( you may want to add a 0.1 mfd cap between
these two pins)
*  A SPDT Microswitch, common connected to MCLR, (pin 1)
     normally closed contact connected to Vss, (pin 8 or pin 19)
     normally open contact connected to + terminal of a 9 volt battery.
- terminal of 9 volt battery connected to Vdd, ( pin 20).  You may not
want a fresh 9 volt battery, the voltage on pin 1 when in normally open
position should be 12-14 volts.  Use an old one from a smoke alarm and replace
it with a fresh one.
*  A 2 foot cable with 3 wires connected to a DB25P printer port plug.
    RB7, (pin 28), thru a 1K resistor to pin 2 of DB25P
    RB6, (pin 27), thru a 1K resistor to pin 3 of DB25P
    Vss, (pin 19) to pin 21 of DB25P

*  Use pp.exe software from pic84v05.zip.  You must use set ppsetup=3
from DOS, (or DOS window?) and use the -n switch because you can't read from
the PIC with this arrangement.

If you don't want to plug the PIC in with the power on, just remove one
of the 1.5 v cells or add an additional microswitch on the - terminal of
the 4.5 v pack.

I've been doing conversions of Cheapic programs to the 16F872.  I've
changed the binary clock to use 1 seven segment LED and used timer 2 and an
external 32 kHz watch crystal allowing the PIC to sleep most of the time.
If you would like a copy of this program, contact me off line at
ockers@anl.gov

Stan

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu