When programming an Atmel microchip over SPI (ISP), what external clocking do I have to provide to programee? Does it have to match programmer's internal clock frequency, or can be totally different because SPI CLK line will be used? If the latter, then are there any limitations on SPI CLK freq I will use on programmer, or will programee auto sync to whatever goes? Also, do I maybe need to disconnect any possible external clock from programee? Also, do I have to set any freq fuses on programee?

I'm newbie to EE, so I'd be grateful for thorough answers.

(For programmer I intend to try using a Raspberry Pi's SPI interface)

edit: uh, yes, I mean an AVR microcontroller, sorry and thanks.

  • \$\begingroup\$ "ATMEL microchip" is pretty broad, but i assume you refer to some 8-bit AVR controller? \$\endgroup\$ – Rev1.0 Aug 23 '13 at 10:09

Assuming you refer to a Atmel AVR micro controller, the only limitation is, that the controllers main clock frequency must be at least 4x the clock speed of the ISP programming frequency.

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  • \$\begingroup\$ yes, avr, thanks. So I must still provide some external/internal clock on the AVR, and then I can divide this freq by 4 and setup SPI on RasPi to something lower, correct? \$\endgroup\$ – akavel Aug 23 '13 at 10:26
  • \$\begingroup\$ @akavel: That is correct. \$\endgroup\$ – Rev1.0 Aug 23 '13 at 10:51

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