# ATmega128 ISP problems

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#### eltonjohn

atmega128 isp

I soldered two ATMega128 chips on development boards and one of the chips had no ISP communication at all. The other worked for some time and it also finnaly quited too.
I also saw that the fuses were programmed and i never did it .
Now i have no more ISP communication .I can't even read the chip's signature .The MISO line appears dead .. Does any one had problems like these? I suspect that the problems come from my programmer . Any suggestions about how to deal with these chips? .Or recomendations on how to avoid problems with the ISP interface.

#### Bingo600

##### Full Member level 5
mega128 isp

@EJ

Are you having anything else connected on the ISP pins ?? , they are also used for uart.

The "Trick" Atmel uses if doing both serial and ISP , is to use a HC4053 , and let /Reset select the ISP.

ISP is for programming the Chip.

If you mean SPI ....
The M128 does not use MISO/MOSI for programming the chip , just for SPI comms.

This is Atmels ref design guidelines
http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf

And their EMC guide
http://www.atmel.com/dyn/resources/prod_documents/doc1619.pdf

Do a search for the schematic of the STK-501 (Atmels M128 Reference board)
Schematic might be here
http://www.atmel.com/dyn/resources/prod_documents/DOC2491.PDF

Or maybe have a look here (a single sided hobbyist board)

Ohh.............

Code:
4 Common mistakes on a new Mega128

1: Dont connect the PEN pin , (you should NOT connect it)

2: It ships from factory with the Mega103 compatibility fuse set
So it's a Mega103 , until you clear that one.

3: It ships from factory with the default 1Mhz internal oscillator enabled
(Fuses again). When programming via ISP , be sure the ISP programmer
frequency is max 1/4 of clockspeed.

4: MISO/MOSI isn't used for programming the chip

/Bingo

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