Re: Charter of newsgroup


Donald Harris wrote:
"linnix" <me@xxxxxxxxxxxxxxxxxx> wrote in message
news:1157036811.432184.292510@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Al wrote:
In article <1156979843.522090.281930@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"linnix" <me@xxxxxxxxxxxxxxxxxx> wrote:

Al wrote:
In article <1156882054.604376.170200@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"linnix" <me@xxxxxxxxxxxxxxxxxx> wrote:

Is this an appropriate newsgroup to submit questions regarding
PICs?

I haven't been able to find any newsgroups listed as such that
are
provided by my ISP.

Al

Definitely. This is the place.

Only if you are willing to ask the same question in an auditorium
full
of 500 experienced engineers.


OK, thanks. I'm overwhelmed by the response.

First question.

I want to use a real time clock for my application. I want to make
the
thing as cheaply as possible so I am looking for the lowlyest (??)
PIC I
can use. I have my sights set on the 12C508A.

What I want to do is use two pins for the RT clock, two for
controlling
an external device, and two for communicating with the PIC from an
external terminal service, yet to be determined.

I know I may not have enough program space to do this, but I'm just
starting.

At any rate, what I want to know is this. A real time clock chip like
the NJU6355 has three pins, CE, a clock and a data I/O. Can I do a
hardware CE and still have full functionality of the RT clock using
just
the clock and I/O pins?

What would your hardware CE be? It must determine the I/O direction
for the PIC to handle it properly. By the way, why can't you implement
the RTC inside the PIC?


As you can see, I run out of PIC pins if I can't.

Al


According to the spec for the RTC, CE HIGH means that I/O is available
and nothing else. So, as I think about it more, I think that I can just
set it HIGH and as long as I am not querying the RTC, I should be
getting nothing out. And if I ask for the day of the week, I should get
that data out.

I could be wrong, but CE determine the direction of the DATA pin.
Forgive me if I read the spec incorrectly.


I'm not attempting to do RTC inside the PIC as I want to use the
cheapest one available, like the 12C508A. And why reinvent the wheel.

There are plenty of software library to implement a clock in PIC, which
would cut the cost (and the RTC chip). You don't have to reinvent it.


Al


The CE input is CHIP ENABLE, NOT Direction!

Oh, yes. I read the wrong table. It should be Ok to pull it high.


Don

.

Relevant Pages

  • Re: Charter of newsgroup
    ... I want to use a real time clock for my application. ... the NJU6355 has three pins, CE, a clock and a data I/O. ... According to the spec for the RTC, CE HIGH means that I/O is available ...
    (comp.arch.embedded)
  • Re: Charter of newsgroup
    ... I want to use a real time clock for my application. ... What I want to do is use two pins for the RT clock, ... the NJU6355 has three pins, CE, a clock and a data I/O. ... According to the spec for the RTC, CE HIGH means that I/O is available ...
    (comp.arch.embedded)
  • Re: Charter of newsgroup
    ... I want to use a real time clock for my application. ... What I want to do is use two pins for the RT clock, ... the NJU6355 has three pins, CE, a clock and a data I/O. ... According to the spec for the RTC, CE HIGH means that I/O is available ...
    (comp.arch.embedded)
  • Re: Charter of newsgroup
    ... I want to use a real time clock for my application. ... What I want to do is use two pins for the RT clock, ... the NJU6355 has three pins, CE, a clock and a data I/O. ... What would your hardware CE be? ...
    (comp.arch.embedded)
  • Re: need small PAL with SR latch
    ... > Its amasing just how many pins some of theses devices have, ... Asynchronous logic and loops in logic are nightmares. ... > Metastable states in asynch loops can cuase nightmares but they still have ... > loops hence the setup and min clock width timings inorder to avoid ...
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