At 09:48 PM 4/13/2004 -0700, you wrote:
>Hi Everyone,
>I don't have any problem to configure the PIC to
>communicate with multiple SPI devices with separate
>SDI and SDO lines.  Now, I come across a so-called
>"SPI compatible" device (TMP124) which has only ONE
>common SDI/SDO line.  How do I interface the PIC to
>this one?  Keep in mind that there are already some
>ICs on the SPI bus.
>Regards,
>Thomas

Minimalist solution is a resistor from SDI to SDO on the MCU. Value
would depend on worst-case bus timing and capacitive loading,
but something like 4.7K..

You'd connect the SO/I line to SDI on the MCU.

You could also use an analog or bus switch to connect SDO to SDI just
when this particular chip is being accessed. For example, the 5 ohm
NC7SZ66 with an inverter or extra port pin, or the NC7SB3157 controlled
directly by the TMP124 /CS line.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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