Aytac, you should take note of Kunal's valid statement about grounding the SPI chip select on your slave device. There are some devices that do not take action until the active-low SPI chip select goes from low (active) to high (inactive). One example is the MAX4820 relay driver. These devices will require a SPI chip select connected to the BF532 (via SPISEL or PFx). In general, it is bad practice to enable the SPI slave all the time, due to this reason and the noise issue I mentioned earlier.

if you have to connect to only one slave, you need to use a PFx (which will
>be connected to ~SPISS of slave)...
>You can not permanently ground the ~SPISS of slave
>~SPISS needs to be toggled for every word access
>and there are some specific timing relation of ~SPISS toggle with SCK
>....
>any specific reason why you are trying to save PFx (after all its just one
>connection)
>???
>On 7/13/06, e...@yahoo.com wrote:
>>
>> Hi All,
>>
>> I will use BF532' SPI connection and I am wondering that
>>
>> If I use one physical SPI connection, Do I need to use PFO(input slave
>> select(SPISS)) or (PF1-PF7 (SPISEL71)) ???
>>
>> I mean if I arrange BF as a master, automatically I won't use PF0 but Do I
>> need to use PF1 for selecting to other device???? althought there is only
>> one device to be selected.
>>
>> Or Only MOSI,MISO and SCK connections are enough to communicate for one to
>> one connection
>>
>> Thanks all
>>
>> Aytac
>>
>--
>That which does not kill, makes us stronger Start a New Thread

Hi All,
>
>I will use BF532' SPI connection and I am wondering that
>
>If I use one physical SPI connection, Do I need to use PFO(input slave select(SPISS)) or (PF1-PF7 (SPISEL71)) ???
>
>I mean if I arrange BF as a master, automatically I won't use PF0 but Do I need to use PF1 for selecting to other device???? althought there is only one device to be selected.
>
>Or Only MOSI,MISO and SCK connections are enough to communicate for one to one connection
>
>Thanks all
>
>Aytac
>

The SPISS is used if there is another SPI master in your system and the BF is acting as slave. Since that is not the case here, you are correct in not using it. You can use the SPISEL pins, or even any other available programmable flag as a general purpose output to act as your SPI chip-select to your slave device (this is what we did in a previous design, see pg 10-12 in '533 HRM), just make sure you get the clock polarity and clock phase correct for your slave device (pg 10-10 in '532 HRM) and check your timing. If you have just one slave device, you'll need to ground its SPI chip select to make it active always; then you can avoid using the SPISEL or general PF on the BlackFin. I would not recommend having the slave device selected all the time, however. Noise spikes on the SCK line could cause erroneous clock pulses to your slave device (like during power up or power down). Even though erroneous clock pulses are probably unlikely, I'd avoid the situation if possible, unless you have run out of available PF pins. Start a New Thread

if you have to connect to only one slave, you need to use a PFx (which will
be connected to ~SPISS of slave)...
You can not permanently ground the ~SPISS of slave
~SPISS needs to be toggled for every word access
and there are some specific timing relation of ~SPISS toggle with SCK
....
any specific reason why you are trying to save PFx (after all its just one
connection)
???
On 7/13/06, e...@yahoo.com wrote:
>
> Hi All,
>
> I will use BF532' SPI connection and I am wondering that
>
> If I use one physical SPI connection, Do I need to use PFO(input slave
> select(SPISS)) or (PF1-PF7 (SPISEL71)) ???
>
> I mean if I arrange BF as a master, automatically I won't use PF0 but Do I
> need to use PF1 for selecting to other device???? althought there is only
> one device to be selected.
>
> Or Only MOSI,MISO and SCK connections are enough to communicate for one to
> one connection
>
> Thanks all
>
> Aytac
>
--
That which does not kill, makes us stronger Start a New Thread

At 06:05 AM 7/13/2006, e...@yahoo.com wrote:
>Hi All,
>
>I will use BF532' SPI connection and I am wondering that
>
>If I use one physical SPI connection, Do I need
>to use PFO(input slave select(SPISS)) or (PF1-PF7 (SPISEL71)) ???
>
>I mean if I arrange BF as a master,
>automatically I won't use PF0 but Do I need to
>use PF1 for selecting to other device????
>althought there is only one device to be selected.
>
>Or Only MOSI,MISO and SCK connections are enough
>to communicate for one to one connection
>
>Thanks all
>
>Aytac

You won't use SPISS. This would be used if the BF was a slave device.

In theory, you could omit the SPISEL line with
only one device as long as the external device
was always enabled. I would probably still use a
SPISEL if it is available so that the slave
device was always deselected when not in use.

Al Clark
Danville Signal Processing, Inc.

>

Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com

Start a New Thread

Hi All,

I will use BF532' SPI connection and I am wondering that

If I use one physical SPI connection, Do I need to use PFO(input slave select(SPISS)) or (PF1-PF7 (SPISEL71)) ???

I mean if I arrange BF as a master, automatically I won't use PF0 but Do I need to use PF1 for selecting to other device???? althought there is only one device to be selected.

Or Only MOSI,MISO and SCK connections are enough to communicate for one to one connection

Thanks all

Aytac Start a New Thread