Byron A Jeff wrote:
> IIRC Olin's EasyProg had a mode where one could send bit-twiddle
> commands
> so that it's possible to program new parts without changing the
> firmware.

This is correct.  The host software can explicitly set Vdd from 0 to 6V, set
Vpp either low or to 13V, set PGC and PGD to logic high or low, set PGD to
high impedence and read its value, and determine whether PGD is being driven
by the target PIC.  In addition there are some slightly higher level
commands that read and write up to 32 bits at a time to/from the target
using the usual clocking scheme.

My software tends to use these low level commands only for one-time
operations where an extra few mS once doesn't matter.  Examples of this are
determining the target PIC type and doing a bulk erase.  When doing the real
programming and verifies it uses the high level interface for speed, but it
is certainly possible to fully manipulate a PIC without them.  I sometimes
do this for testing when implementing a new programming algorithm.

It just occurred to me that it should be possible to modify the host
software for one of the directly connected parallel or serial port
programmers to send low level EasyProg commands instead.  These programs
already have all the logic to wiggle the lines.  One would only need to
intercept the direct writes to the port and emit EasyProg commands instead -
at least if the software was well structured in the first place (probably a
big if).  I guess the advantage would be getting access to PICs supported by
these programs that aren't supported by the normal EasyProg software.  No,
I'm not offering to do this, but if anyone is interested I can provide some
support.


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