AD7606/AD7606-6/AD7606-4
CS
CS
takes the bus out of three-state and clocks
The falling edge takes the data output lines, DOUTA and DOUTB,
The falling edge of
out the MSB of the 16-bit conversion result. This MSB is valid
CS
out of three-state and clocks out the MSB of the conversion
result. The rising edge of SCLK clocks all subsequent data bits
on the first falling edge of the SCLK after the
falling edge.
CS
onto the serial data outputs, DOUTA and DOUTB. The
input
The subsequent 15 data bits are clocked out of the AD7606/
AD7606-6/AD7606-4 on the SCLK rising edge. Data is valid on
the SCLK falling edge. To access each conversion result, 16 clock
cycles must be provided to the AD7606/AD7606-6/AD7606-4.
can be held low for the entire serial read operation, or it can be
pulsed to frame each channel read of 16 SCLK cycles. Figure 46
shows a read of eight simultaneous conversion results using two
D
OUT lines on the AD7606. In this case, a 64 SCLK transfer is used
The FRSTDATA output signal indicates when the first channel,
CS
to access data from the AD7606, and is held low to frame the
entire 64 SCLK cycles. Data can also be clocked out using just
one DOUT line, in which case it is recommended that DOUTA be
used to access all conversion data because the channel data is
output in ascending order. For the AD7606 to access all eight
conversion results on one DOUT line, a total of 128 SCLK cycles
CS
V1, is being read back. When the input is high, the FRSTDATA
output pin is in three-state. In serial mode, the falling edge of
CS
takes FRSTDATA out of three-state and sets the FRSTDATA
pin high, indicating that the result from V1 is available on the
DOUTA output data line. The FRSTDATA output returns to
a logic low following the 16th SCLK falling edge. If all channels
are read on DOUTB, the FRSTDATA output does not go high when
V1 is being output on this serial data output pin. It goes high
only when V1 is available on DOUTA (and this is when V5 is
available on DOUTB for the AD7606).
CS
is required. These 128 SCLK cycles can be framed by one
signal, or each group of 16 SCLK cycles can be individually
CS
framed by the
signal. The disadvantage of using just one
DOUT line is that the throughput rate is reduced if reading occurs
after conversion. The unused DOUT line should be left unconnected
in serial mode. For the AD7606, if DOUTB is to be used as a single
READING DURING CONVERSION
Data can be read from the AD7606/AD7606-6/AD7606-4 while
BUSY is high and the conversions are in progress. This has little
effect on the performance of the converter, and it allows a faster
throughput rate to be achieved. A parallel, parallel byte, or serial
read can be performed during conversions and when oversampling
may or may not be in use. Figure 3 shows the timing diagram for
reading while BUSY is high in parallel or serial mode. Reading
during conversions allows the full throughput rate to be achieved
when using the serial interface with VDRIVE above 4.75 V.
D
OUT line, the channel results are output in the following order:
V5, V6, V7, V8, V1, V2, V3, and V4; however, the FRSTDATA
indicator returns low after V5 is read on DOUTB. For the AD7606-6
and the AD7606-4, if DOUTB is to be used as a single DOUT line,
the channel results are output in the following order: V4, V5, V6,
V1, V2, and V3 for the AD7606-6; and V3, V4, V1, and V2 for
the AD7606-4.
Figure 6 shows the timing diagram for reading one channel of
CS
data, framed by the
AD7606-4 in serial mode. The SCLK input signal provides the
CS
signal, from the AD7606/AD7606-6/
Data can be read from the AD7606 at any time other than on
the falling edge of BUSY because this is when the output data
registers are updated with the new conversion data. Time t6, as
outlined in Table 3, should be observed in this condition.
clock source for the serial read operation. The
goes low to
access the data from the AD7606/AD7606-6/AD7606-4.
CS
64
SCLK
D
D
A
B
V1
V5
V2
V6
V3
V7
V4
V8
OUT
OUT
Figure 46. AD7606 Serial Interface with Two DOUT Lines
Rev. 0 | Page 28 of 36
ADI [ ADI ]
