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SD16 Fundamentals

Started by Richard August 16, 2007
I am having trouble using the SD16 in a msp430f423. I would like to
verify the following:

There are three separate ADCs in this device

Each ADC can select one of three input channels (Can multiple ADCs
select the same channel??)

The output registers SD16MEMx correspond to the ADC, not the physical
input channel.

Are these assumptions correct?

Thansk

Rich

Beginning Microcontrollers with the MSP430

--- In m..., "Richard" wrote:
>
> I am having trouble using the SD16 in a msp430f423. I would
> like to verify the following:
>
> There are three separate ADCs in this device

Yes. And I think they call these three separate ADCs as
Channel-0, -1, and -2

> Each ADC can select one of three input channels (Can multiple
> ADCs select the same channel??)

No. I think each ADC is a "channel". There are 3 channels.

> The output registers SD16MEMx correspond to the ADC, not the
> physical input channel.

These registers store the result of the conversions. There are
digital. The physical input channels are analog.
I am still confused. If each ADC is a "channel" and it is associated
with only one set of differential pair inputs, then why have an input
pair MUX, controlled by SD16INCHx in SD16INCTLx?

Does ADC Channel zero always place it's results in SD16MEM0, channel
one in SD16MEM1, etc?

Thanks

Rich

--- In m..., "old_cow_yellow"
wrote:
>
> --- In m..., "Richard" wrote:
> >
> > I am having trouble using the SD16 in a msp430f423. I would
> > like to verify the following:
> >
> > There are three separate ADCs in this device
>
> Yes. And I think they call these three separate ADCs as
> Channel-0, -1, and -2
>
> > Each ADC can select one of three input channels (Can multiple
> > ADCs select the same channel??)
>
> No. I think each ADC is a "channel". There are 3 channels.
>
> > The output registers SD16MEMx correspond to the ADC, not the
> > physical input channel.
>
> These registers store the result of the conversions. There are
> digital. The physical input channels are analog.
>
--- In m..., "Richard" wrote:
> I am still confused. If each ADC is a "channel" and it is
> associated with only one set of differential pair inputs,
> then why have an input pair MUX, controlled by SD16INCHx
> in SD16INCTLx?

It is confusing! Each of the three channels is mux'ed to 8
pairs of differential signals. They are called A0.0, A0.1,
..., A0.7 for channel-0, A1.0, A1.1, ..., A1.7 for channel-1,
and A2.0, A2.1, ..., A2.7 for channel-2.

But only A0.0, A1.0, and A2.0 are brought to the pins that
can be connected to the outside world. A0.6, A1.6, and A2.6
can be used for the temperature sensor inside the chip.
A0.7, A1.7 and A2.7 are shorts for checking zero-offset.
All other 15 pairs are unusable!

>
> Does ADC Channel zero always place it's results in SD16MEM0, channel
> one in SD16MEM1, etc?

Yes.
So if each of the three channels are MUX'd to A0.0-1, A1.0-1, and
A2.0-1, and temperature, why can't I select the same physical input
pair with two seperate ADC "channels"? The mux is controled by
seperate SFRs particular to each channel, but there is only one set of
physical inputs!

Rich

--- In m..., "old_cow_yellow"
wrote:
>
> --- In m..., "Richard" wrote:
> > I am still confused. If each ADC is a "channel" and it is
> > associated with only one set of differential pair inputs,
> > then why have an input pair MUX, controlled by SD16INCHx
> > in SD16INCTLx?
>
> It is confusing! Each of the three channels is mux'ed to 8
> pairs of differential signals. They are called A0.0, A0.1,
> ..., A0.7 for channel-0, A1.0, A1.1, ..., A1.7 for channel-1,
> and A2.0, A2.1, ..., A2.7 for channel-2.
>
> But only A0.0, A1.0, and A2.0 are brought to the pins that
> can be connected to the outside world. A0.6, A1.6, and A2.6
> can be used for the temperature sensor inside the chip.
> A0.7, A1.7 and A2.7 are shorts for checking zero-offset.
> All other 15 pairs are unusable!
>
> >
> > Does ADC Channel zero always place it's results in SD16MEM0, channel
> > one in SD16MEM1, etc?
>
> Yes.
>
OK, so I think I get it. Channel0 is mux'd to 8 channeles 0.0-0.7,
where only 0.0-0.1 exists in this part. The sames follows for the
other three channels.
So, although there is an input MUX, it will always be set to 0 for
channel0, 1 for channel1, and 2 for channel 2 (in this device).

Is this correct?

Rich
--- In m..., "Richard" wrote:
>
> So if each of the three channels are MUX'd to A0.0-1, A1.0-1, and
> A2.0-1, and temperature, why can't I select the same physical input
> pair with two seperate ADC "channels"? The mux is controled by
> seperate SFRs particular to each channel, but there is only one set of
> physical inputs!
>
> Rich
>
> --- In m..., "old_cow_yellow"
> wrote:
> >
> > --- In m..., "Richard" wrote:
> > > I am still confused. If each ADC is a "channel" and it is
> > > associated with only one set of differential pair inputs,
> > > then why have an input pair MUX, controlled by SD16INCHx
> > > in SD16INCTLx?
> >
> > It is confusing! Each of the three channels is mux'ed to 8
> > pairs of differential signals. They are called A0.0, A0.1,
> > ..., A0.7 for channel-0, A1.0, A1.1, ..., A1.7 for channel-1,
> > and A2.0, A2.1, ..., A2.7 for channel-2.
> >
> > But only A0.0, A1.0, and A2.0 are brought to the pins that
> > can be connected to the outside world. A0.6, A1.6, and A2.6
> > can be used for the temperature sensor inside the chip.
> > A0.7, A1.7 and A2.7 are shorts for checking zero-offset.
> > All other 15 pairs are unusable!
> >
> > >
> > > Does ADC Channel zero always place it's results in SD16MEM0, channel
> > > one in SD16MEM1, etc?
> >
> > Yes.
>