Treatment for FS pin

Shunsuke Nagata

Part Number: ADS8557
Other Parts Discussed in Thread: TMS320F28375D

Hi, team,

I have a question for ADS8557 FS pin. Could you please support this?

I will use SDO_A with SEL_A=1, SEL_B = SEL_C = 0. The figure 37 in datasheet has timing chart as below. Should host set FS pin to high in every 16 SCLK? Or Should user keep FS pin low during CHA0 to CHC1?

And Is there a documentation which explain how to treat for FS pin?

Regards,
Nagata.

over 5 years ago

0 Tom Hendrick over 5 years ago

TI__Guru**** 168735 points

Hi Nagata-san,

The 'dashed' line in Figure 47 implies that the FS pin would not need to toggle for each of the three (or six) 16-bit transfers depicted there. It really depends on your processor and how your software handles the transfer. Which controller are you planning to use? Documentation should be available with the DSP peripheral on how this setup works.

0 Shunsuke Nagata over 5 years ago in reply to Tom Hendrick

TI__Genius 12240 points

Hi, Tom -san,

Thank you very much for your support. The host controller is C2000 (TMS320F28375D). Do you have a documentation to control ADS8557?

Regards,
Nagata.

0 Shunsuke Nagata over 5 years ago in reply to Shunsuke Nagata

TI__Genius 12240 points

Tom -san,

Here is additional question. MCU usually has SOMI and SIMO pins for SPI. If user use ADS8557 as hardware mode, SDI pin at ADS should connect to GND and SOMI of MCU should be connect SDO_x of ADS. In this case, SIMO of MCU doesn't need to connect ADS. Is my understanding correct?

Regards,
Nagata.

0 Tom Hendrick over 5 years ago in reply to Shunsuke Nagata

TI__Guru**** 168735 points

FS is the 'Frame Sync' associated with the Multi-channel Buffered Serial Port (McBSP). You can define the word and frame size as needed.

0 Tom Hendrick over 5 years ago in reply to Shunsuke Nagata

TI__Guru**** 168735 points

McBSP uses DX (i.e. SIMO) and DR (i.e. SOMI). If you are not transmitting data to the ADS8557, there is no need to connect DX to anything.

C2000™︎ microcontrollers

C2000 microcontrollers forum

Treatment for FS pin