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Thread: F876 programming questions
www.piclist.com/techref/microchip/devprogs.htm?key=programming
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face BY : Mike Mansheim email (remove spam text)



I'm trying to move from using a promate to understanding the programming
process and burning chips with my own setup (for now, working with an
F876, NOT using LVP).  So far, I've used Microchip's documentation and
I've got questions.  Generally, can anyone recommend a good detailed
description of this process that I can get my hands on?
Specifically:
The progamming spec says that programming mode is entered while holding
RB6 & 7 low while raising MCLR from Vil to Vihh (which needs to happen
within 72 osc clocks).  Vil is defined in the F876 data sheet as the
"input low" voltage; essentially ground.  However, when watching the
promate operate on a scope (working with the micro in-circuit), MCLR
and Vdd come up together to 3-5V for 10's of milliseconds, then MCLR is
bumped to 13V to go into programming mode.  So I'm wondering what exactly
the requirements are to enter programming mode.  Can a "running" chip
enter programming mode just by having MCLR raised?  If so, what are the
72 osc clocks relative to?
Regarding the "read data" command, the timing diagram shows that the data
line is an output for the last 15 bits of the data string.  However, when
I do this, I always show the last bit being a "1", when the data string is
supposed to be "0", data(14), "0".  Is this ok? Or should I revert for the
last bit and assert the "0"?
Sorry for the long post, and thanks for any help.

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