User`s manual

programming are inputs in target system then separation
by resistors is sufficient and resistors make a low pass filter
too. If pins are outputs, then use of resistors saves a
programming time. Of course the isolation resistors R1, R2,
(R3) can be replaced by switches or jumpers, if necessary.
In that case, during the ISP programming of target device
the switches (jumpers) must be open. But the using of
switches (jumpers) adds a next manipulation time to
programming procedure.
Example of application note
Microcontrollers Atmel AVR and AT89Sxxx series
This application note is used in 849. This interface corresponds
with Atmel application note AVR910: In-System Programming.
This application note describes the recommended ISP
interface connector layout in target system (top view).
1
2
34
56
Vcc
RESET
MISO
SCK MOSI
GND
Description of required pins for in-system programming
by AVR910.
Pin Name Comment
SCK Serial Clock Programming clock, generated by the In-
System programmer (master).
MOSI Master Out – Slave In Communication line from In-System
programmer (master) to target MCU
being programmed (slave).
MISO Master In – Slave Out Communication line from target MCU
(slave) to In-System programmer
(master).
GND Common Ground The two systems must share the same
common ground.
RESET Target MCU Reset To enable In-System programming, the
target MCU Reset must be kept active.
To simplify this, the In-System
programmer should control the target
MCU Reset
Vcc Target Power To allow simple programming of targets
operating at any voltage, the In-System
programmer can draw power from the
target. Alternatively, the target can have
power supplied through the In-System
programming connector for the duration
of the programming cycle
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