SPP: IN-CIRCUIT 16F84 PROGRAMMER
                    ================================

                              David Tait
                        david.tait@man.ac.uk
                     http://www.man.ac.uk/~mbhstdj


The programming software in spp.exe is a version of pp.exe (see
pic84v05.zip in my PIC archive: http://www.man.ac.uk/~mbhstdj/files).
The operation of the program is described in program.txt found in
pic84v05.zip.  The hardware (H/W) required can be any of the designs 
shown in:

   direct.pcx           direct connection to parallel or serial port
   parpic.pcx           reset control and read back via parallel port
   serpic.pcx           reset control and read back via serial port

See use.pcx and target.pcx for an overview of the connections between
the PC, programmer and PIC target board.

The hardware setup should be communicated to the software via the 
environment variable PPSETUP as follows:

   PPSETUP=p0  parallel port using DIRECT or PARPIC H/W (default)
   PPSETUP=p1  parallel port plus inverting buffers
   PPSETUP=s0  serial port using DIRECT H/W or SERPIC without buffers
   PPSETUP=s1  serial port using SERPIC H/W
   
The port used is set by:

   PPLPT=nn    use LPTnn (default LPT1) for parallel port H/W
   PPCOM=nn    use COMnn (default COM1) for serial port H/W
   
If PPDEBUG=1 a debugging mode is entered that can be used to confirm
correct setup and toggle the interface lines one-by-one.

Use PPDELAY=nn to add nn*0.83 microseconds delay between port accesses.
The valid range is nn between 0 and 127 (default 6).

The easiest way to use the program is via a batch file that sets
the environment variables required before running spp.  The batch
file myspp.bat gives an example for SERPIC hardware on COM1.  

The DIRECT hardware requires the user to put the PIC into programming
mode manually and run spp with the -n (no read) switch (the
description in qandd.txt from pic84v05.zip applies to this hardware).

The PARPIC and SERPIC H/W automate things a little but still require the
user to connect the programming voltage (VPP); this can either be done
using a switch on the the target board - see target.pcx - or by connecting 
+12V-14V to the /MCLR connection via a 1k-10k resistor (the optional
VPP supply components shown in parpic.pcx and serpic.pcx mean voltages
up to 18V or so can be used, for example, a couple of small 9V batteries
in series).  The PARPIC and SERPIC hardware allow the user to read the 
PIC contents and run/reset a program under PC control (the batch file 
reset.bat shows how to use spp to reset the PIC assuming SERPIC H/W on 
COM1).

Example: to download walk.hex to a 16F84 using DIRECT H/W on COM2 the
following must be run (either directly or from a batch file):

   set ppcom=2
   set ppsetup=s0
   spp -n walk.hex

when spp asks for the programming voltage to be applied, ground /MCLR
by closing the reset switch, connect +12V-14V to /MCLR via a 1k-10k 
resistor and then open the reset switch.  Hit any key to program the 
PIC and when spp exits close the reset switch, remove the +12V-14V 
connection and finally open the reset switch.

Only the PARPIC and SERPIC H/W will produce correct results for hex
files that specify both program and data memory.  If data memory must
be programmed using the DIRECT H/W it should be in a file of its own.

More information can be found here:

http://www.man.ac.uk/~mbhstdj/icp84.html


V-0.1  26 April 1998