Owner manual

The recommendation for design of target system with ISP
programmed device
The target system must be designed to allow all signals, which are use for In-system
programming to be directly connected to ISP programmer via ISP connector. If target system
use these signals for other function, is necessary isolated these signals. Target system
mustn’t affect these signals during In-system programming.
For in-system programmable devices manufacturers publish application notes. Design of B+K
PRECISION programmers together with respect of these application notes allows proper In-
system programming. Condition is exactly respecting these application notes. Applications
notes, which B+K PRECISION use in ISP programmers, are published in
www.bkprecision.com, section Support / Application Notes.
Please, read some notes for following recommended circuits.
• Purpose of D1 diode is to protect the target circuit against a higher voltage, which is
provided by ISP programmer.
• If your target board supply differs from mentioned 5V, choose please the Zener diode (D1)
voltage according to this supply voltage.
• We recommend to use resistors R1, R2, (R3) to separate the target device from target
system. If pins needed for ISP 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 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).
B+K PRECISION’s recommended circuit for ATMEL AVR:
ISP connector target device target system
reset circuit
R2
R3
GND
C1
22n
GND
VCC
GND
D2
1N4148
GND
R11
100k
C2
1u/10V
VCC
SCK
MISO
RESET
GND
I1
AT ME L AV R
DATA OUT
SCK
RESET
R1
MOSI
DATA IN
GND
target VCC check only
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