Datasheet

AD7280A
Rev. 0 | Page 41 of 48
Example 4: Convert and Read a Single Voltage
or Auxiliary ADC Input Result from One Part
In this example, it is assumed that all AD7280As in the daisy
chain have been initialized to their correct device addresses.
1.
The register address corresponding to the voltage or
auxiliary ADC input result to be read should be written to
the read register of the part to be read (see Table 13 for
register addresses). In this example, the Cell Voltage 6
register result is read from Device 3 in the stack. The 32-bit
write command is 0xC382865A (see Table 2 6, Write 1).
2.
Set Bits[D13:D12] of the control register to 1 on all parts.
This setting turns off the read operation on all parts. The
32-bit write command is 0x01B617EA (see Table 2 6,
Write 2).
3.
Set Bits[D13:D12] of the control register of the part to be
read from such that the required voltage is read back. With
the exception of a self-test conversion, it is not possible to
convert on a single channel; six, nine, or 12 conversions must
be completed. This example reads a voltage conversion from
Device 3 in the stack; therefore, Bit D14 and Bit D12 of the
control register should be set to 0, and Bit D15 and Bit D13
should be set to 1 on Device 3. The 32-bit write command
is 0xC1B400FA (see Table 26, Write 3).
4.
Program the
CNVST
control register to 0x02 on Device 3
to allow conversions to be initiated using the
CNVST
pin
on that part. The 32-bit write command is 0xC3A0417A
(see , Write 4). Table 26
5.
Initiate conversions through the falling edge of
CNVST
.
6.
Allow sufficient time for all conversions to be completed
plus t
WA I T
.
7.
Program the
CNVST
control register to gate the
CNVST
signal on all parts. The 32-bit write command is
0x03A0340A (see , Write 5). This write prevents
unintentional conversions from being initiated by noise or
glitches on the
Table 26
CNVST
pin. This write also updates the on-
chip output registers of all devices in the daisy chain.
8.
Apply a
CS
low pulse that frames 32 SCLKs to read back
the desired voltage or auxiliary ADC result. This frame
should simultaneously write the 32-bit command
0xF800030A, as described in the section
(see , Write 6).
Serial Interface
Table 26
Note that when reading from a single device in a stack of
AD7280As, the SCLK frequency must be lower than 1 MHz
to read back the register data from parts higher in the chain
than the master device.
Table 26. Example 4: Converting and Reading a Single Voltage or Auxiliary ADC Result from One AD7280A Device
Write Command Device Address Register Address Data Write All D11 8-Bit CRC D2 to D0
32-Bit Write
Command
Write 1 11000 011100 00010100 0 0 11001011 010 0xC382865A
Write 2 00000 001101 10110000 1 0 11111101 010 0x01B617EA
Write 3 11000 001101 10100000 0 0 00011111 010 0xC1B400FA
Write 4 11000 011101 00000010 0 0 10000111 010 0xC3A0417A
Write 5 00000 011101 00000001 1 0 10000001 010 0x03A0340A
Write 6 11111 000000 00000000 0 0 01100001 010 0xF800030A