ADS127L01 registers access via spi daisy-chain

Konstantin Sumenko60

Other Parts Discussed in Thread: ADS127L01

Hello just want to clarify the ADS127L01 register access via spi in a daisy chain connection. Suppose I have 3 ADC's in a daisy-chain. Am i right:

1) I can do a mass write to all ADC's with all there nCS pins tied low (just like in a regular multi slave topology).

2) I can do a single ADC register write tying its nCS low while other ADC's nCS pins are held high (just like in a regular multi slave topology).

3) I can do a mass single byte register read from all ADC's in a chain with all nCS pins tied low:

- First: I do a mass write with a register address and 1 byte for read setting

- Second: I read 3 bytes from topmost ADC in a chain

Thanks!

over 9 years ago

0 Ryan Andrews over 9 years ago

TI__Guru 66706 points

Hello Konstantin,

For Daisy-Chained Devices in SPI Mode, you will be able to write to all device registers at once, but you can only read the register values from the first device in the chain.

Writing to multiple daisy-chained devices in SPI Mode can be done exactly as you described in 1) - DIN, /CS, and SCLK are tied together and you simply treat the chain as a "one device." Alternatively, you may write to one device at a time using the individual /CS pins (2).

However, with daisy-chained devices, you cannot do a mass register read as in 3). During a register read, the data that comes into the DAISYIN pin is gated and will not shift out on the DOUT pin. Therefore, you will only be able to read the register data from the first device in the chain.

Best Regards,

0 Konstantin Sumenko60 over 9 years ago in reply to Ryan Andrews

Prodigy 210 points

Ryan, it's importnat note on a mass read in a daisy-chaine mode, thank you.

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ADS127L01 registers access via spi daisy-chain