Sorry for the late reply but I just learned about the list yesterday :) Not sure how to reply to a message in the archive.
[Q1] The "5V" pin is the "VCC" pin. It is connected to the VCC of the uC. For some boards this is 5V (or a little less). For a lot of boards (like my wiblocks boards) this is 3.3V. The voltage will be constant during programming. [Q2] I program all my parts using the ICSP. An oscillator is not required. [Q3] You can run the ATmega168/328 at frequencies up to 20MHz. However, the maximum frequency is dependent on the VCC you use for the microcontroller. There is a frequency derating curve in the datasheet. I believe the reason that the Arduino is run at 16MHz is to give some margin with the VUSB + LDO dropout. I run my boards at 3.3V and 12MHz. The CPU frequency is set in the Makefile using the F_CPU variable. You will not have problems with most of the code. However, there could me some libraries, like NewSoftSerial, that could have nested if/then/else clauses that do not examine the F_CPU for the frequency you choose. I had a customer who wanted to use NewSoftSerial with his wiblocks board. After calculating the new timing constants I was able to modify NewSoftSerial to work at 12MHz. See http://wiblocks.luciani.org/docs/app-notes/software-serial.html (* jcl *) -- http://www.wiblocks.com
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