Hi all,

I know that PIC programmers was a frequently discussed matter lately. Anyway
I have some questions:

I need a programmer suitable for In Circuit Programming of all PICs of the
16Cxx-family. I suppose that a programmer must meet the following
specifications:
* The MCLR pin must be configured tristate: hi impedance for normal operation
(MCLR connected to Vdd via ~1k), active low, and active programming voltage
* the Vdd pin should be active 5 V or hi impedance for normal op.
* CLK and DATA pin connected to programmer or hi impedance.

Some background:
all pins should be configurable to hi imp. so that the programmer can stay
connected while the PIC is working in normal operation mode.
The MCLR pin must provide active low to override any resistors between MCLR
and Vdd from the target circuit, and it must provide a low impedance
programming voltage with the necessary programming current (for all PICs but
the 16C84).


Which one is a suitable programmer?



Some words about available programmer hardware:
* The H. Schaer programmer
this is the first and only serial programmer I use at the moment (only for
16C84). At this programmer the MCLR pin is either not connected or active low or
passive VIA 10k at the programming voltage. I am afraid that this configuration
is not capable of sourcing the necessary programming current for PICs, except
the 16C84. Result: Unsuitable for 16Cxx

* The D. Tait programmer
this programmer can connect the MCLR directly to Vpp or via 10k to GND.
Due to the missing active low level and hi impedance: Unsuitable for InCircuit
Programming

* The AN589 programmer
this programmer has an intelligent solution to provide the MCLR with all
necessary voltage levels, but the 5V Vdd cannot be switched off (yet).

I came to the conclusion that the AN589 programmer is the most suitable
universal InCircuit programmer. I thought of adding two transistors to apply
the 5V to the PIC only when MCLR is tied to GND or to Vpp. My PIC application
normally runs at 3 V, but accepts 5 V supplied externally by the programmer,
that is the reason why the 5V of the programmer should be switched off after
programming.


Any comments / better programmer hardware / correction of my statement?



SIS / Antti offers a universal software for these programmers which I wanted
to use. The PIP-2 programmer has the GO function to let a 16C84 run in
normal mode after programming. What is behind this 'undocumented feature'?


Siggi


Siegfried Grob,                                   |
student of electrical engineering,                |
university of ulm, germany                        |
e-mail:  siegfried.grob@student.uni-ulm.de        |
tel&fax: +49 731 25148                            |
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