ad73311 Analog Devices, Inc., ad73311 Datasheet - Page 15

• Manufacturer Part Number: ad73311
• Description: Low Cost, Low Power Cmos General Purpose Analog Front End
• Manufacturer: Analog Devices, Inc.

SPORT Register Maps
There are two register banks for the AD73311: the control
register bank and the data register bank. The control register
bank consists of five read/write registers, each 8 bits wide. Table
IX shows the control register map for the AD73311. The first
two control registers, CRA and CRB, are reserved for control-
ling the SPORT. They hold settings for parameters such as bit
rate, internal master clock rate and device count (used when
more than one AD73311 is connected in cascade from a single
SPORT). The other three registers; CRC, CRD and CRE are
used to hold control settings for the ADC, DAC, Reference and
Power Control sections of the device. Control registers are
written to on the negative edge of SCLK. The data register
bank consists of two 16-bit registers that are the DAC and
ADC registers.
Master Clock Divider
The AD73311 features a programmable master clock divider
that allows the user to reduce an externally available master
clock, at pin MCLK, by one of the ratios 1, 2, 3, 4 or 5 to pro-
duce an internal master clock signal (DMCLK) that is used to
calculate the sampling and serial clock rates. The master clock
divider is programmable by setting CRB:4-6. Table VI shows
the division ratio corresponding to the various bit settings. The
default divider ratio is divide by one.
MCD2
0
0
0
0
1
1
1
1
Table VI. DMCLK (Internal) Rate Divider Settings
MCD1
0
0
1
1
0
0
1
1
REGISTER A
CONTROL
MCLK
(EXTERNAL)
SE
RESETB
SDIFS
SDI
MCD0
0
1
0
1
0
1
0
1
8
DIVIDER
MCLK
3
REGISTER B
CONTROL
DMCLK
(INTERNAL)
DMCLK Rate
MCLK
MCLK/2
MCLK/3
MCLK/4
MCLK/5
MCLK
MCLK
MCLK
8
SERIAL REGISTER
SERIAL PORT
REGISTER C
(SPORT)
CONTROL
8
Serial Clock Rate Divider
The AD73311 features a programmable serial clock divider that
allows users to match the serial clock (SCLK) rate of the data to
that of the DSP engine or host processor. The maximum SCLK
rate available is DMCLK and the other available rates are:
DMCLK/2, DMCLK/4 and DMCLK/8. The slowest rate
(DMCLK/8) is the default SCLK rate. The serial clock divider
is programmable by setting bits CRB:2–3. Table VII shows the
serial clock rate corresponding to the various bit settings.
DAC Advance Register
The loading of the DAC is internally synchronized with the
unloading of the ADC data in each sampling interval. The de-
fault DAC load event happens one SCLK cycle before the
SDOFS flag is raised by the ADC data being ready. However,
this DAC load position can be advanced before this time by
modifying the contents of the DAC Advance field in Control
Register E (CRE:0–4). The field is five-bits wide, allowing 31
increments of weight 1/(DMCLK/8); see Table VIII. In certain
circumstances this can reduce the group delay when the ADC
and DAC are used to process data in series. Appendix E details
how the DAC advance feature can be used.
NOTE: The DAC advance register should be changed before
the DAC section is powered up.
DA4
0
0
0
—
1
1
*DMCLK = 16.384 MHz.
8
DA3
0
0
0
—
1
1
REGISTER D
Table VII. SCLK Rate Divider Settings
SCD1
0
0
1
1
CONTROL
Table VIII. DAC Timing Control
DIVIDER
DA2
0
0
0
—
1
1
SCLK
2
SCD0
0
1
0
1
8
DA1
0
0
1
—
1
1
SDOFS
SCLK
REGISTER E
CONTROL
SDO
DA0
0
1
0
—
0
1
DMCLK/8
DMCLK/4
DMCLK/2
DMCLK
SCLK Rate
AD73311
Time Advance*
0 ns
488.2 ns
976.5 ns
—
14.64 µs
15.13 µs