ADBMS2950BCCSZ datasheet(25/97 Pages) AD

25 / 97 page

Data Sheet

ADBMS2950B

Rev. 0 | Page 25 of 97

Daisy-Chain Polling

In a daisy-chain configuration of N stacked devices, the same

two polling methods can be used.

If the bottom device communicates in SPI mode, the SDO of

the bottom device indicates the operation status of the entire

stack. For example, SDO remains low until all the devices in the

stack complete the operations.

In the first method of polling, after an ADC conversion

command is sent, clock pulses are sent on SCK while keeping

CSB low. The SDO status becomes valid only at the end of 2 × N

clock pulses on SCK and is updated for each clock pulse that

follows (see Figure 25).

In the second method, the PLADC command is sent followed

by clock pulses on SCK while keeping CSB low. Similar to the

first method, the SDO status is valid only after 2 × N clock

cycles on SCKI and is updated after each clock cycle that follows

(see Figure 26).

If the bottom device communicates in isoSPI mode, then isoSPI

data pulses are sent to the device to update the operation status.

On the serial controller side, where the ADBMS682x is used,

this action is achieved by clocking the SCK pin. The operation

status is valid only after the bottom ADBMS2950B device

receives 2 × N isoSPI data pulses, and the status is updated for

each isoSPI data return pulse that follows. The device returns a

low data pulse if any of the devices in the stack is busy

performing operations and returns a high data pulse if all the

devices completed conversions.

Figure 25. SDO Polling After an ADC Conversion Command (Daisy-Chain Configuration)

Figure 26. SDO Polling Using PLADC Command (Daisy-Chain Configuration)

Command Codes Overview

Table 33 lists all available commands of the ADBMS2950B.

Details for each command are described in the following

chapters organized in functional groups. Additional

ADBMS6830B compatible commands are listed in Table 87.

Table 33. Command Codes Overview

Name

Type

BIT

BIT 9

BIT 8

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

Description

SRST

CMD

Software reset, including

CCNT reset (ADBMS6830B:

SRST).

RSTCC

CMD

Reset Command Counter

(ADBMS6830B: RSTCC).

SNAP

CMD

Freeze result registers

(ADBMS6830B: SNAP).

UNSNAP

CMD

Unfreeze result registers

(ADBMS6830B: UNSNAP).

ADI1

CMD

OPT[3]

OPT[2]

OPT[1]

OPT[0]

Start I1ADC and VB1ADC

(ADBMS6830B: ADCV).

ADI2

CMD

OPT[3]

OPT[2]

OPT[1]

OPT[0]

Start I2ADC and VB2ADC

(ADBMS6830B: ADSV).

ADV

CMD

OW[1:0]

VCH[3:0]

Start V1ADC and V2ADC.

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