3.3.4.2.1 Connecting to an AVR SPI Target
The recommended pinout for the 6-pin SPI connector is shown in AVR SPI Pinout.
Connection to a 6-pin 100-mil SPI Header
Use the AVR 6-pin adapter board to connect to a standard 100-mil SPI header.
Connection to a 6-pin 50-mil SPI Header
Use the AVR 6-pin mini adapter board to connect to a standard 50-mil SPI header.
The SPI interface is effectively disabled when the debugWIRE Enable (DWEN) fuse is programmed, even if the SPIEN fuse is also programmed. To re-enable the SPI interface, the ‘disable debugWIRE’ command must be issued while in a debugWIRE debugging session. Disabling debugWIRE in this manner requires that the SPIEN fuse is already programmed. If MPLAB X IDE fails to disable debugWIRE, it is probably because the SPIEN fuse is NOT programmed. If this is the case, it is necessary to use a high-voltage programming interface to program the SPIEN fuse.
The SPI interface is often referred to as “ISP” since it was the first in-system programming interface on Microchip AVR products. Other interfaces are now available for in-system programming.