spi interface!! pls help!!!!

[ashish sharma]

Dear board mates,
actually i am interfacing my mcu (atmega32l) with my asic and in the same circuit i am using the spi bus lines for my isp (in system programming) ...

Now the situation is that when i try to program my mcu ( in an external target board using stk500) with asic present on the same chip it doesnt enter in the programming mode however if the asic is not present then i am able to program my mcu

can you please tell me the solution of how to program with asic on the board as without asic my whole circuit would be nothing but silicon dirt

Note : my lock bit settings are that of default one that's no locking on memory , boot ,and application and my fuse settings are default with internal 1 MHZ oscillator clock ( as the stk500 board can provide up to 3.6 MHZ internal oscillations)

waiting for your responses as i am struck!

Regards
Ashish

 

[artem]

Connect ASIC output ports through resistors and ISP connector pins directly to avr32l inputs .

 

[umup]

All SPI slaves (like your ASIC) must switch off their outputs (to Z-state) when slave select signal (SS) = 1. In RESET mode all pins of ATMega configured as inputs. So you need to put pull-up resistor on the SS pin to switch off ASIC, so its output will not interfere with programming data.

 

[suresh_ecer]

hi
i dont have seen your schematic but i suggest u to check your reset pin.
u have connect 2k2 register and 0.1uf cap to reset pin?
if this is ok then see the status of your reset pin while mega32 trying to enter
in prog mode.it should go low.then check status of miso and mosi pin.
then try with pullup on isp pin.

 

[ashish sharma]

Thanks guys ,,, i solved my problem by my own and it was solved by placing two 10k resistors in the path of MOSI and MISO of asic and the isp pins ...so as to avoid the drive contention...involved as these pins are connecting mcu , ,,asic,,,and isp directly.... but after it occur then i found that artem said almost the same ....so i am pressing the helped me button for him...thanks you all too for your responses...

 

[umup]

10k may be too much, can be problems on high speeds, 2K is better

 

[artem]

I would recommend these articles from atmel :
AVR040: EMC Design Considerations
http://www.atmel.com/dyn/resources/prod_documents/doc1619.pdf
AVR042: AVR Hardware Design Considerations
http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf

Good luck

 

[ashish sharma]

Umup, for your query,,, i must tell you that i have used a jumper to place 10k resistor in within the lines when the isp programming is going on for the mcu... so that the asic will be isolated totally and hence 10 k would be a plus point rather than a negative one and after programming that's in the normal operation the jumper could be removed so as the spi lines couldnt see any resistance between asic and mcu....

and artem thanks for refering these articles ...but i already have them.....

 

[kaustubhkhole]

can any one pls post good books on SPI interface ?

 

[umup]

There are no specific books about SPI, all information available in microcontroller datasheet in SPI section