AD7280ABSTZ datasheet(38/48 Pages) AD

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AD7280A

Rev. 0 | Page 38 of 48

EXAMPLES OF INTERFACING WITH THE AD7280A

The AD7280A supports a number of read options. The user can

read back the results from

•

All conversions completed on all parts in the chain

•

Individual registers on all parts in the chain

•

Individual registers on selected parts in the chain

In each case, the user must first write to the read register on the

selected parts to configure that part to supply the correct data

on the outputs. When reading back an individual register, the

address of that register should be written to the read register of

the selected part. When reading back conversion results from

any or all parts in the chain, an address of 0x00 should be written

to the read register of the selected parts.

When the address written to the read register is 0x00, the

conversion results selected for readback are controlled by

setting Bits[D13:D12] of the control register (see Table 14).

These bits allow the user to select one of four different read-

back options:

•

Read back 12 conversion results: six voltage and six

auxiliary.

•

Read back nine conversion results: six voltage and three

auxiliary.

•

Read back six conversion results: six voltage results only.

•

Switch off the read operation on this part.

To read back an individual register from a single AD7280A in

the daisy chain, follow these steps:

On all other parts in the chain, set Bits[D13:D12] of the

control register to 11 to select the no-read operation on

those parts.

On the targeted part, set Bits[D13:D12] of the control

Note that it is more efficient in terms of 32-bit write cycles to

first switch off the read operation on all AD7280As in the daisy

chain. This is achieved with a single write cycle, using Bit D12

in the write command to address all parts in the chain. The user

can then address the individual part and set Bits[D13:D12] of

the control register to turn on the read operation for that part.

CONVERT AND READBACK ROUTINE

When conversion data from any or all of the AD7280As in a

daisy chain is read back, the conversion results returned from

the AD7280A are the last completed set of conversions on that

part. It is recommended that the user also set Bits[D15:D14] of

the control register to select the number of conversions to be

completed on each part and initiate the conversions through

either the CNVST pin or the rising edge of CS as part of the

read operation. In this way, the user can implement a simple

convert and readback routine with the most efficient number

of 32-bit write and read operations.

A general example of this routine, which converts and reads

back from all parts in the AD7280A daisy chain, is as follows:

Write 0x00 to the read register on all parts in the daisy

chain. Note that 0x00 is the default value of this register

on power-up and following a software reset operation.

Write to the control register on all parts. Set Bits[D15:D14]

to select the required conversions. Set Bits[D13:D12] to

select the required conversion results for readback.

Initiate the conversions through either the falling edge of

CNVST or the rising edge of CS (set Bit D11 of the control

Allow sufficient time for each conversion to be completed

plus tWAIT. See the Converting Cell Voltages and Auxiliary

ADC Inputs section.

Apply a CS low pulse that frames 32 SCLKs for each

conversion result to be read back.

EXAMPLES

The following examples of conversion and/or readback routines

can be used in an application that implements a chain of AD7280A

devices to monitor the voltage and/or auxiliary ADC inputs of

the AD7280A on a stack of lithium ion batteries.

AD7280ABSTZ Datasheet(PDF) 38 Page - Analog Devices

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