EVAL-AD7933CB AD [Analog Devices], EVAL-AD7933CB Datasheet - Page 25

• Manufacturer Part Number: EVAL-AD7933CB
• Description: 4-Channel, 1.5 MSPS, 12-Bit and 10-Bit Parallel ADCs with a Sequencer
• Manufacturer: AD [Analog Devices]

AD7933/AD7934
Reading Data from the AD7933/AD7934
With the W/ B pin tied logic high, the AD7933/AD7934
interface operates in word mode. In this case, a single read
operation from the device accesses the conversion data-word on
Pins DB0/DB2 to DB11. The DB8/HBEN pin assumes its DB8
function. With the W/ B pin tied to logic low, the
AD7933/AD7934 interface operates in byte mode. In this case,
the DB8/HBEN pin assumes its HBEN function. Conversion
data from the AD7933/ AD7934 must be accessed in two read
operations with 8 bits of data provided on DB0 to DB7 for each
of the read operations. The HBEN pin determines whether the
read operation accesses the high byte or the low byte of the12-
or 10-bit word. For a low byte read, DB0 to DB7 provide the
eight LSBs of the 12-bit word. For 10-bit operation, the two
LSBs of the low byte are 0s and are followed by 6 bits of
conversion data. For a high byte read, DB0 to DB3 provide the
4 MSBs of the 12-/10-bit word. DB4 of the high byte is always 0
and DB5 and DB6 of the high byte provide the Channel ID.
Figure 37
shows the read cycle timing diagram for a 12-/10-bit
DB0 TO DB7
Figure 38. AD7933/AD7934 Parallel Interface—Read Cycle Timing for Byte Mode Operation (W/ B = 0)
HBEN/DB8
RD
CS
t
t
13
15
t
10
LOW BYTE
t
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12
t
11
t
16
t
14
transfer. When operated in word mode, the HBEN input does
not exist and only the first read operation is required to access
data from the device. When operated in byte mode, the two read
cycles shown in F
word from the device.
The CS and RD signals are gated internally and level triggered
active low. In either word mode or byte mode, CS and RD may
be tied together as the timing specification t
minimum. The data is placed onto the data bus a time t
both CS and RD go low. The RD rising edge can be used to latch
data out of the device. After a time, t
become three-stated.
Alternatively, CS and RD can be tied permanently low and the
conversion data will be valid and placed onto the data bus a
time, t
t
17
9
, before the falling edge of BUSY.
t
15
HIGH BYTE
igure 38
Preliminary Technical Data
are required to access the full data-
t
16
14
, the data lines will
10
and t
11
is 0 ns
13
after