MPLAB SNAP to Atmega1280&81 Connection?

[Rjc987]

Hey guys, complete newbie with AVR and the snap (used to PIC & Pickit3 so trying to recalibrate my brain…) - the snap user guide is pretty slim and some of the information seems contradictory. Just trying to interface a system I’m working on with mplab x ide and dump the rom etc. My target board has JTAG and ISP headers, jtag is standard atmega pinout, and the ISP is apparently using the AVR ICE pinout standard with rx tx scl sda and icp1 (see diagrams below). The snap guide connection table (included below) says the pinout for the snap is mclr, vdd, ground, PGD, PGC, then “do not connect” for pin 6, and “unused for icsp” for pins 7&8, but the table that translates between different protocols and chip families, under ACR JTAG, shows pins 2-8 all used, with reset on pin 6 vs mclr on pin 1, and I don’t see anything that equates to the ISP header I have on the board, although data stream cdc on the next page shows 7&8 as rx and tx. I also read elsewhere that reset is supposed to be disconnected for debugging but that’s contradictory to the diagram. So for jtag do I follow the table and connect everything, or everything BUT pin 6, or everything up to pin 5 or pin 6? And what do I connect for the ICE version of the ISP connector? Very confused.

Also does anyone have any idea what the solder thru holes marked rx tx sdi sck etc are for? Are they able to be used as inputs instead of the header or?

Thanks!

[ataradov]

Connect as described in the table. The text next to the drawing if for MIPS devices.

The pins on the SNAP itself are not useful for anything, they are just for debugging of the SNAP itself.