RX6110SA RTC with ATMEGA 4 wire SPI

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Has anyone got this Epson RTC running with SPI?.

 

The RX6110SA I'm using does not go tristate on MISO during slave reception of byte.

 

Very difficult to understand the Jinglish  application manual for this chip to establish the exact requirements for initialisation but as the MISO is not acting correctly, I suspect its a bad chip.

 

If anyone can confirm that they have actually run in SPI mode (SPISEL tied high) then its clearly a hardware issue. 

 

Running it with the great little AT90USB1287.

 

Thanks

 

John

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How are you handling the CE pin ?

Most SPI devices have an active-low /CS pin

Your RX6110SA has an active-high CE pin

 

Looking at the SPI Timing waveforms,   DO shoul be hi-Z when CE is inactive.

 

David.

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Hi David,

 

I am selecting with active high.  DO just shows a clock output whenever I clock in and the chip is CE high. when I deselect the chip CE (low) the output on DO stops. Thus I conclude the RTC is generating the DO output and not some short somewhere else.

 

Am getting another chip - they are a bit difficult to neatly remove from the board, but a new one should shed some light on the issue?

 

John

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I would simply write to the RX6110 registers with SPI.    Then try reading them back.    This should be pretty straightforward.

 

Likewise,   you can communicate with other SPI devices that are on the same bus.    Note that the 'usual' problem is not making the SS pin an output.   Thus initiating haywireability.

 

You can test the 3-state of MISO even if you don't have any other SPI devices.    Connect a 47k resistor from MISO to a GPIO output pin.

Then read the MISO pin when the GPIO is high and low.

 

David.

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Thanks for that David.

 

Got a very fast response from Epson Europe today who deduced that the SPI select line was in fact not high and the chip was behaving as though it was in I2C mode.

On examination this proved to be the case (dry joint).

All working fine now. Great to have such support from Epson.

 

John

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Go on.    That must have been a very dry joint.

 

I am pleased that you have got it working.

 

David.