Datasheet
AD5410/AD5420 Data Sheet
Rev. F | Page 18 of 32
where N is the total number of AD5410/AD5420 devices in the
chain. When the serial transfer to all devices is complete,
LATCH is taken high. This latches the input data in each device
in the daisy chain. The serial clock can be a continuous or a
gated clock.
A continuous SCLK source can be used only if LATCH is taken
high after the correct number of clock cycles. In gated clock
mode, a burst clock containing the exact number of clock cycles
must be used, and LATCH must be taken high after the final
clock to latch the data. See Figure 4 for a timing diagram.
CONTROLLER
DATA IN
LATCH
SDIN
SCLK
DATA OUT
SERIAL CLOCK
CONTROL OUT
SDO
LATCH
SCLK
SDO
LATCH
SCLK
SDO
SDIN
SDIN
*ADDITIONAL PINS OMITTED FOR CLARITY.
AD5410/
AD5420*
AD5410/
AD5420*
AD5410/
AD5420*
07027-035
Figure 39. Daisy Chaining the AD5410/AD5420
Readback Operation
Readback mode is invoked by setting the address byte and read
address as shown in Table 9 and Table 8 when writing to the
input shift register. The next write to the AD5410/AD5420
should be a NOP command, which clocks out the data from the
previously addressed register, as shown in Figure 3. By default,
the SDO pin is disabled. After having addressed the AD5410/
AD5420 for a read operation, a rising edge on LATCH enables
the SDO pin in anticipation of data being clocked out. After the
data has been clocked out on SDO, a rising edge on LATCH
disables (tristate) the SDO pin once again. To read back the
data register, for example, the following sequence should be
implemented:
1. Write 0x020001 to the AD5410/AD5420 input shift
register. This configures the part for read mode with the
data register selected.
2. Follow this with a second write, a NOP condition, 0x000000.
During this write, the data from the data register is clocked
out on the SDO line.
Table 8. Read Address Decoding
Read Address Function
00 Read status register
01 Read data register
10 Read control register
Table 9. Input Shift Register Contents for a Read Operation
MSB LSB
DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 to DB2 DB1 DB0
0 0 0 0 0 0 1 0 X
1
Read address
1
X = don’t care.