In-System Programming Overview - Equinox Systems Micro-ISP IV Series User Manual

It is possible to In-System Program (ISP) members of the Atmel AVR microcontroller by
utilising a serial programming algorithm based around the popular SPI 3-wire bus protocol.
The Micro-ISP programmer implements ISP of these devices by generating the necessary SPI
programming waveforms under control of PC software. In order to place the target device
into programming mode, it is necessary to assert the RESET pin of the target microcontroller.
SPI Master/Slave definitions
The Micro-ISP programmer operates on the principle that during any programming operation
the programmer is the SPI Master and the target device to be programmed is the SPI Slave.
Micro-ISP Programmer ............. SPI Bus Master
Target ISP Microcontroller(s) ... SPI Bus Slave(s)
This status is only the case during ISP. The target microcontroller can be a master or slave
during program execution (i.e. when it is programming code). The programmer tri-states off
the SPI bus when not programming.
Typical Hardware Configuration for In-System Programming (ISP) Mode
PC
PC Ground
Micro-ISP

In-System Programming Overview

MICRO-ISP
Programmer
IV User Manual V2.03
Series
Common earth point
18
RST
Target
MOSI
System
MISO
SCK
Target Ground