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'[pic] PIC16F610'
2008\08\11@190130 by ýrt

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Hello,

I'm trying to find the right pic for my trivial RTC application. Looks
like PIC16F610 is the cheapest pic with right number of IOs (that I
need) and a 16 bit timer. In the datasheet there is no mention of it
being in the nanowatt family but if I search of nanowatt devices,
microchip's site lists pic16f610 as nanowatt device.

Has anyone played with this device?

I have gone through Jinx's and BAJ's  posts about using pic's timer 1
for RTC. Very good information there.

Thanks.


--
ìrt

2008\08\11@204814 by Jinx

face picon face
> like PIC16F610 is the cheapest pic with right number of IOs

The 16F54 is half the price and has 12 I/O also

Most PIC's quiescents are quite similar @ 32kHz, if that's what's
used for timing, whether they're nanowatt or standard

12F675 9uA
16F88 9uA
18F1320 13uA
16F870 20uA

The 16F610 is average at 13uA at comparable Vcc. That's potentially
100,000 hours (11 years) from 1.3Ah AAs, with the PIC fully awake


2008\08\11@211418 by ýrt

picon face

On Mon, Aug 11, 2008 at 5:46 PM, Jinx <spam_OUTjoecolquittTakeThisOuTspamclear.net.nz> wrote:

>
> The 16F54 is half the price and has 12 I/O also

But no timer1 :-(


--
Cheers,

ìrt

2008\08\11@212804 by Dr Skip

picon face


ìrt wrote:
> On Mon, Aug 11, 2008 at 5:46 PM, Jinx <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:

>  > The 16F54 is half the price and has 12 I/O also
>
> But no timer1 :-(
>

Because "time is money"  ;)

2008\08\11@220808 by Jinx

face picon face
> > The 16F54 is half the price and has 12 I/O also
>
> But no timer1 :-(

Er, um, I knew that

;-))

But it does have TMR0, and that's all you need for RTC. If the PIC
is awake anyway, counting TMR0 interrupts uses no more power
than if you were using a 16-bit timer

2008\08\12@010230 by ýrt

picon face

On Mon, Aug 11, 2008 at 7:07 PM, Jinx <joecolquittspamKILLspamclear.net.nz> wrote:
>> > The 16F54 is half the price and has 12 I/O also
>>
>> But no timer1 :-(
>
> Er, um, I knew that
>
> ;-))
>
> But it does have TMR0, and that's all you need for RTC. If the PIC
> is awake anyway, counting TMR0 interrupts uses no more power
> than if you were using a 16-bit timer

That is correct, if I use tmr0 then I have to use main system clock
and can't use a 32768Hz watch crystal and that means that I have to
keep the controller alive all the time.

Sorry I didn't mentioned earlier that I wish to power it with a
battery of 2x 1.5 AAA. Wake up every 2 secs (no timer1 preload with
0x800000), update the time registers and go to sleep for two secs.
That's the reason why I was looking at nanowatt.

--
Cheers,
ìrt

2008\08\12@025232 by Jinx

face picon face

> Sorry I didn't mentioned earlier that I wish to power it with a
> battery of 2x 1.5 AAA. Wake up every 2 secs (timer1 preload
> with 0x800000), update the time registers and go to sleep for two
> secs. That's the reason why I was looking at nanowatt

Ah, I see

Still, 19uA isn't too much of a draw. But I know what you mean
about nanowatt. I've some 12F675s that have been doing a
monitoring job for three years on 3 AA, mostly sleeping, and the
battery voltage hasn't budged

2008\08\12@032522 by ýrt

picon face

On Mon, Aug 11, 2008 at 11:44 PM, Jinx <.....joecolquittKILLspamspam.....clear.net.nz> wrote:
> Ah, I see
>
> Still, 19uA isn't too much of a draw. But I know what you mean
> about nanowatt. I've some 12F675s that have been doing a
> monitoring job for three years on 3 AA, mostly sleeping, and the
> battery voltage hasn't budged

If you still think it is doable with a F54, I can read more about
implementing the RTC using TMR0. Most of the information that I read
about implementing RTC on a pic was with TMR1.

In my previous post I meant no preload of 0x800000 to get 2 secs. A
preload will get me 1 sec interrupt. Am I correct?

--
Cheers,
ìrt

2008\08\12@061644 by Jinx

face picon face
> If you still think it is doable with a F54, I can read more about
> implementing the RTC using TMR0

It's certainly doable, but I'm not really trying to influence you as to
which PIC to use

> In my previous post I meant no preload of 0x800000 to get 2 secs.
> A preload will get me 1 sec interrupt. Am I correct?

At 32768Hz, whether that's TMR1OSC or the core frequency for
the whole chip, a free-running 8-bit timer will roll over at 128Hz, and
a 16-bit timer at 0.5Hz (as you said, 2s). So re-loading a 16-bit with
$8000, or simply setting TMR1H,7 at roll over time, will make it 1Hz

Your primary concern is, understandably, battery lifetime, rather than
how the RTC is clocked. TMR1OSC is the least consuming option for
the 16F610. d/s says 7uA for TMR1 module on + operating current.
When sleeping, operating current is 150nA, which is negligible compared
with TMR1's useage

When woken, operating current very much depends on core frequency.
You'd have to determine the awake power used when the PIC wakes
up to do what you want

For example, if the code takes 100 cycles and core speed is 4MHz,
then the PIC wll be awake for 100us. At 4MHz, operating current is
360uA => an extra 36nW over sleep power. If core speed was 8MHz,
the power used would be 50us * 620uA = 31nW over sleep power.
Sleep power, which is the vast majority, 99.995%, of the 1s, is only
7nW

So basically, drain is the 7.15uA for sleep and TMR1OSC. If you
have AAA alkalines with 1.2Ah (1,200,000uAh) capacity, you'd be
looking at a lifetime of 19 years for a 16F610, ignoring I/O loads

2008\08\12@080114 by olin piclist

face picon face

ìrt wrote:
> In the datasheet there is no mention of it
> being in the nanowatt family but if I search of nanowatt devices,
> microchip's site lists pic16f610 as nanowatt device.

It's silly to worry about what marketing name somone hung on a particular
PIC.  Look at the datasheet and see how much current the part draws in sleep
mode with timer 1 oscillator running.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\08\13@014008 by ýrt

picon face

Thanks for the pointers Jinx, Olin.

I appreciate your comments and suggestions.


2008/8/12 Olin Lathrop <EraseMEolin_piclistspam_OUTspamTakeThisOuTembedinc.com>:
> It's silly to worry about what marketing name somone hung on a particular
> PIC.  Look at the datasheet and see how much current the part draws in sleep
> mode with timer 1 oscillator running.



--
Cheers,
ìrt

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