How did you determine that it doesn`t work? What value is received (0x00, 0xff, ..?).

When i wire both lines i always recive 0x00. When mosi/miso are connected rtc chip is not responding. I think that the chips cannot (sorry) interferate with each other becos of CS lines. So my assumption was placed on connection betwen data lines.

If you sure that the problem is because two wires are tied together then you should solve it with using open-drain buffer for MOSI (either with SN7407 or with transistors).

I`m not sure but take a look at this:
http://www.maxim-ic.com/appnotes....number/427
is that it ? (soft controlled dir)

Maybe MCU utilizes strong pull-up for alternative functions of a pin, maybe not. I have no such info.

I dont understand. Processor ovverides any pin config in case of use spi (when enabled), and spi is alternete functions of this pins.

Another solution is to replace hardware SPI receiver with software routine...
Too much cost for processor with hardware spi.

Thanks
Lucas Bajger