Datasheet

AD7280A
Rev. 0 | Page 39 of 48
Example 1: Initialize All Parts in a Daisy Chain on Initial
Power-Up and When Coming Out of Power-Down
Example 1 shows a typical device initialization routine.
1.
To initialize all device addresses, set Bit D2 and Bit D0
of the control register to 1, and set Bit D1 of the control
register to 0 on all parts in the chain. The 32-bit write
command is 0x01C2B6E2 (see Table 23, Write 1).
2.
Write the register address corresponding to the lower byte
of the control register to the read register on all parts. The
32-bit write command is 0x038716CA (see Table 23, Write 2).
3.
Apply a
CS
low pulse that frames 32 SCLKs for each device
in the chain to be read back. All conversion readbacks
should simultaneously write the 32-bit command
0xF800030A, as described in the section
(see , Write 3). This read is used to verify that all
AD7280As in the chain have received and locked their
unique device addresses. Confirm that all device addresses
are in sequence.
Serial Interface
Table 23
Example 2: Convert and Read All Parts, All Voltages,
and All Auxiliary ADC Inputs
In this example, it is assumed that all AD7280As in the daisy
chain have been initialized to their correct device addresses.
1.
Write Register Address 0x00 to the read register on all
parts. A device address of 0x00 is used when computing
the CRC for commands to write to all parts. The 32-bit
write command is 0x38011CA (see Table 24, Write 1).
Note that 0x00 is the default value of the read register on
power-up and after a software reset; therefore, this write
operation may not be necessary.
2.
Set Bits[D15:D12] of the control register to 0 on all parts.
The 32-bit write command is 0x01A0131A (see Table 24,
Write 2).
Note that this is the default value of Bits[D15:D12] of the
control register on power-up and after a software reset;
therefore, this write operation may not be necessary.
3.
Program the
CNVST
control register to 0x02 on all parts
to allow conversions to be initiated using the
CNVST
pin.
The 32-bit write command is 0x03A0546A (see ,
Write 3).
Table 24
4.
Initiate conversions through the falling edge of
CNVST
.
5.
Allow sufficient time for all conversions to be completed
plus t
WA I T
. Following the completion of all conversions,
apply a
CS
low pulse that frames 32 SCLKs for each conver-
sion result to be read back. The 32-bit write command is
0xF800030A, as described in the section
(see , Write 4).
Serial Interface
Table 24
Table 23. Example 1: Initializing All AD7280A Devices in a Daisy Chain
Write Command Device Address Register Address Data Write All D11 8-Bit CRC D2 to D0
32-Bit Write
Command
Write 1 00000 001110 00010101 1 0 11011100 010 0x01C2B6E2
Write 2 00000 011100 00111000 1 0 11011001 010 0x038716CA
Write 3 11111 000000 00000000 0 0 01100001 010 0xF800030A
Table 24. Example 2: Converting and Reading All Voltages and All Auxiliary ADC Inputs from All AD7280A Devices
Write Command Device Address Register Address Data Write All D11 8-Bit CRC D2 to D0
32-Bit Write
Command
Write 1 00000 011100 00000000 1 0 00111001 010 0x038011CA
Write 2 00000 001101 00000000 1 0 01100011 010 0x01A0131A
Write 3 00000 011101 00000010 1 0 10000101 010 0x03A0546A
Write 4 11111 000000 00000000 0 0 01100001 010 0xF800030A