SV: [Icc-avr] Maxim MAX6917 alarm problem

[Steven Lose]

Hi Andy.

Doesn't use this RTC my self but had a look in the datasheet.
The ALM output is open drain and active low.

If your HW does not have a pull-up resistor, make sure that you have enabled the pull-up in the uP.
The ALM output stays low until you clear it by SW, so make sure that your int4 clears the alarm, or the input is edge triggered, if cleared somewhere else.

If you have an oscilloscope, it should be easy to verify that a correct signal is there, or even with a standard meter hence the signal stays low.
(Just don't clear it by SW, so you can se the transition on the meter)

Med venlig hilsen / Best regards / mit freundlichen Grüßen

EC POWER A/S

Steven Lose

Software Ingeniør

Tlf.: +45 87434100

Direkte tlf. +45 58286608

Email: sl at ecpower.dk

www.ecpower.dk

-----Oprindelig meddelelse-----
Fra: icc-avr-bounces at imagecraft.com [mailto:icc-avr-bounces at imagecraft.com] På vegne af Andy Syms
Sendt: 2. oktober 2007 18:36
Til: Discussion list for ICCAVR and ICCtiny Users. You do NOT needtosubscribeto icc-announce if you are a member of this.
Emne: [Icc-avr] Maxim MAX6917 alarm problem

Hi

We're having trouble with the alarm on a MAX6917 I2C uP Supervisor/RTC
device.

I2C comms to the device is working fine and we can read/write all RTC
registers. The ALM output of the MAX6917 is connected directly to the INT4
(PE4) input of a Mega2560 with internal pullup enabled.

We just can't get this beast to generate an interrupt, either at a specific
time, or even once per second.

We've tried this on three different boards and my h/w guy (who's just shoved
off on holiday) assures me that the design is good and that the boards are
not faulty.

Any gotchas I'm missing ?  Or other suggestions ?

TIA.

Andy.

--

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>
>>  Andy Syms        Technosoft Systems Ltd
>>
>>     email : asyms at technosoft.co.uk
>>     website : www.technosoft.co.uk
>>
>>       tel : +44 (0) 1483 799554
>>       fax : +44 (0) 1483 799664
>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


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