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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>Interrupt</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/23709/interrupt</link><description> 
Hello guys, can I monitor interrupt0 of 8051 by any h/w means like
by LED or something? I have connected RTC DS12887 IRQ to INT0 however
I couldn&amp;#39;t see logic 1 on DMM 
 </description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/149890?ContentTypeID=1</link><pubDate>Thu, 17 Jul 2008 07:08:25 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:76312ab5-e053-4d69-9175-13673a0d5adf</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
Thanks guys for your valuable support - The project is working
fine Just needed to do was read the register C of RTC on the
occurrence of interrupt&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/149409?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 12:17:39 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:3f525f0e-2383-4dda-9417-d22b9456ac72</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;So does it mean I need to exclusively read C register even if I
serve the IRQ interrupt&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Your interrupt service routine (running on the 8051) needs to read
the C register of the RTC chip. How to do this is described in the
datasheet of the RTC.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/150312?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 08:35:34 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:d7726a33-82a2-485c-a47c-722da5412b00</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
Even this routine doesn&amp;#39;t trig ISR&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/149891?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 08:32:57 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:9d80dc3f-c7a9-48d5-ba5f-e1319f365a15</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
Ok so I&amp;#39;ll try putting XBYTE[0x0C] in my interrupt routine.&lt;/p&gt;

&lt;p&gt;
but I thought after servicing IRQ it would be ok no to read
0x0C&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/149419?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 08:19:20 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:1939ffec-bf52-40c9-a931-26556f8b410c</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
Ya Westermark without connecting dallas chip 89c51 int0 pin is
high&lt;br /&gt;
but as soon as I connect IRQ of DS12887 to INT0 of at89c51 the signal
goes down (low level) so what does it mean?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/149410?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 08:17:23 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:b1548fad-971d-4e1f-8aba-fe5f1a408d95</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
I don&amp;#39;t need what you mean by &amp;quot;exclusively read&amp;quot;.&lt;/p&gt;

&lt;p&gt;
The chip can generate three different interrupts.&lt;/p&gt;

&lt;p&gt;
How can you &amp;quot;service&amp;quot; an interrupt, unless you read the status
register to check which interrupt source (or sources) that generated
the interrupt?&lt;/p&gt;

&lt;p&gt;
How do you expect the chip will know that you have &amp;quot;serviced&amp;quot; the
interrupt if you have a one-way communication, i.e. you only let the
interrupt line trig your ISR, but you do not perform any action to
report back to the Dallas chip that it may deactivate the interrupt
line?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/148931?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 08:12:37 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:461dd4d7-111e-4371-bdeb-17b15e84ddba</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
More from datasheet (generally everybody may know):-&lt;/p&gt;

&lt;p&gt;
&lt;b&gt;&lt;i&gt;The IRQ pin is an active low output of the DS12887 which can
be used as an interrupt input to a processor. The IRQ output remains
low as long as the status bit causing the IRQ is present and
corresponding interrupt enable bit is present.To clear the IRQ pin
processor program generally reads the C register&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;

&lt;p&gt;
So does it mean I need to exclusively read C register even if I
serve the IRQ interrupt&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/135455?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 08:08:19 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:23909fbf-cf07-41af-ad46-943f6156ad5c</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
If your C51 provides internal pull-up, then you do not need to add
an external pull-up resistor.&lt;/p&gt;

&lt;p&gt;
But as mentioned by Christoph Franck: You must make sure that your
C51 does not drive the signal low.&lt;/p&gt;

&lt;p&gt;
The Dallas chip can only sink the signal to ground. Without the
chip connected, the processor pin should be high. If it isn&amp;#39;t, then
your processor hasn&amp;#39;t support for an internal pull-up, or you haven&amp;#39;t
correctly configured your processor to activate the pull-up. Or you
have instructed the C51 to drive the signal low.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/124814?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 07:55:51 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:3df7d877-2579-4663-b40b-b4de5f950920</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;b&gt;&lt;i&gt;When no interrupts are present, IRQ levels used to be in
high impedance state (mentioned in one of the datasheets)&lt;/i&gt;&lt;/b&gt;
that explains why I couldn&amp;#39;t get logic high on that line, am I
correct?&lt;/p&gt;

&lt;p&gt;
&lt;b&gt;&lt;i&gt;multiple number of interrupting devices can be connected to
IRQ bus. The IRQ bus is open drain output and requires external pull
up resistor&lt;/i&gt;&lt;/b&gt;&lt;/p&gt;

&lt;p&gt;
So does it mean I need to include a pull up resistor on that
line?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/124810?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 07:49:18 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:9b6b7b50-bff2-4d85-9234-88d7aaad752a</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;no actually RTC gives interrupt only when current time matches
with predefined/alarm time&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Ok, I&amp;#39;ve dug out the data sheet for the part, and if I understand
it correctly, this statement is not correct. The part has three
different interrupt sources that can all lead to IRQ being set to low
(active).&lt;/p&gt;

&lt;p&gt;
&lt;i&gt;anyway the zero on IRQ of RTC stays only for short amount of
time(transient)&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
That is also incorrect, according to the data sheet IRQ stays low
until the control register C is read.&lt;/p&gt;

&lt;p&gt;
Oh, and make sure that the 8051 isn&amp;#39;t pulling the port pin to low
(i.e. don&amp;#39;t set the latch for the pin to 0).&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/124807?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 07:44:52 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:f6d640d6-cca2-4013-b280-255677024cfa</guid><dc:creator>ImPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
The interrupt output is open-drain, i.e. it will basically
tristate when not signaling an interrupt. Have you remembered to
connect a pull-up resistor?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/114117?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 07:25:54 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:d9eff539-55c3-4c9e-a774-242a169f0ec9</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
no actually RTC gives interrupt only when current time matches
with predefined/alarm time and I&amp;#39;m checking the voltage at the system
start up still i can get is 0V and i double checked it. anyway the
zero on IRQ of RTC stays only for short amount of time(transient)&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/100897?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 07:18:18 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:74e3786d-752b-4a2e-b63e-ab4f25bfcdee</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;but I however I can see is 0V&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
I&amp;#39;m not all that familiar with that particular RTC device, but
could it be that it is already signaling an interrupt and waiting for
it to be serviced ?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/76494?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 06:56:54 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:163f9029-5383-4ad6-895d-93f92278485b</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
Thanks Franck Here is what I think - 1. Interrupts are just
transient changes 2. And AT89C51 requires active low interrupts i.e.
0V - logic 0 So I hope whenever I connect DMM on link between DS12887
IRQ and INT0, I should see high voltage logic1&lt;br /&gt;
but I however I can see is 0V&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/52035?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 06:38:26 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:f3664046-9da5-4f7b-bfec-823c65ba195f</guid><dc:creator>Christoph Franck</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;Hello guys, can I monitor interrupt0 of 8051 by any h/w means
like by LED or something?&lt;/i&gt;&amp;lt;p&amp;gt;&lt;/p&gt;

&lt;p&gt;
Well, if you&amp;#39;re measuring with a multimeter, you&amp;#39;re already trying
to monitor by h/w means. If a multimeter can correctly resolve fast
transients like IRQ signals is another question - the usual way of
monitoring signals like this would be using an oscilloscope if
available.&lt;/p&gt;

&lt;p&gt;
A LED could be used, too, depending on how long the interrupt line
stays active/inactive. A current-limiting resistor might be
necessary.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Interrupt</title><link>https://community.arm.com/thread/52040?ContentTypeID=1</link><pubDate>Tue, 15 Jul 2008 06:33:57 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:f54e0666-7120-4bf3-bd1c-b7ab7846b7b8</guid><dc:creator>Pratik Mahajan</dc:creator><description>&lt;p&gt;&lt;p&gt;
One more thing its at89c51&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>