AD6634BC/PCB Analog Devices Inc, AD6634BC/PCB Datasheet - Page 45

• Manufacturer Part Number: AD6634BC/PCB
• Description: BOARD EVAL SGNL PROCESS AD6634
• Manufacturer: Analog Devices Inc

Specifications of AD6634BC/PCB

• Rohs Status: RoHS non-compliant
• Module/board Type: Evaluation Board
• For Use With/related Products: AD6634
• Lead Free Status / Rohs Status: Not Compliant

In order to access the Input/Output Port Registers, Bit 5 of
SLEEP register (on external memory map) should be written
high. The CAR is then written with the address to the correct
Output Port Register.
0x08 Port A Control Register
Bit 0 enables the use of interpolating half-band filter corresponding
to Port A. Half-band A can be used to interleave the data streams
of multiple channels and interpolate by two providing a maximum
output data rate of 4 the chip rate. It can be configured to
listen to all four channels; channels 0, 1, 2, 3; channels 0, 1, 2;
channels 0, 1; or only channel 0. Half-band A is bypassed when bit
0 = 1, in which case the outputs of the RCFs are directly sent to
the AGC. The channel data streams are still interleaved with the
half-band bypassed, but they are not filtered and interpolated. The
maximum data rate from this configuration would be 2 the
chip rate.
0x09 Port B Control Register
Bit 0 enables the use of interpolating half-band filter corresponding
to Port B. Half-band B can be used to interleave the data streams
of multiple channels and interpolate by 2 providing a maximum
output data rate of 4 the chip rate. It can be configured to
listen to channels 2 and 3; or only channel two. Half-band B is
bypassed when bit 0 = 1, in which case the outputs of the RCFs
are directly sent to the AGC. The channel data streams are still
interleaved with the half-band bypassed, but they are not filtered
and interpolated. The maximum data rate from this configura-
tion would be 2 the chip rate.
0x0A AGC A Control Register
This 8-bit register controls features of the AGC A. The bits are
defined below:
Bits 7–5 define the output word length of the AGC. The output
word can be 4–8, 10, 12, or 16 bits wide. The control register
bit representation to obtain different output word lengths is
given in the Memory Map Table.
Bit 4 of this register sets the mode of operation for the AGC.
When this bit is 0, the AGC tracks to maintain the output signal
level and when this bit is 1, the AGC tracks to maintain a con-
stant clipping error. Consult the AGC section for more details
about these modes.
Bits 3–1 are used to configure the synchronization of the AGC.
The CIC decimator filter in the AGC can be synchronized to an
external sync signal to output an update sample for the AGC error
calculation and filtering. This way the AGC gain changes can be
synchronized to an external block like a Rake receiver. Whenever
an external sync signal is received, the hold-off counter at 0x0B
is loaded and begins to count down. When the counter reaches
one, the CIC filter dumps an update sample and starts working
towards a new update sample. The AGC can be initialized on
each SYNC or only on the first SYNC.
Bit 3 is used to issue a command to the AGC to SYNC immedi-
ately. If this bit is set, the CIC filter will update the AGC with a
new sample immediately and start operating towards the next
update sample. The AGC can be synchronized by the microport
control interface using this method.
Bit 2 is used to determine whether the AGC should initialize on
a SYNC or not. When this bit is set, the CIC filter is cleared and
new values for CIC decimation, number of averaging samples,
CIC scale, Signal gain G
loaded. When Bit 2 = 0, the above-mentioned parameters are
REV. 0
S
, gain K, and pole parameter P are
–45–
not updated and the CIC filter is not cleared. In both cases, an
AGC update sample is output from the CIC filter and the
decimator starts operating towards the next output sample
whenever a SYNC occurs.
Bit 1 is used to ignore repetitive synchronization signals. In
some applications, the synchronization signal may occur peri-
odically. If this bit is clear, each synchronization request will
resynchronize the AGC. If this bit is set, only the first occur-
rence will cause the AGC to synchronize and will update AGC
gain values periodically depending on the decimation factor of
the AGC CIC filter.
Bit 0 is used to bypass the AGC section, when it is set. The
23-bit representation from interpolating half-band filters is still
reduced to a lower bit width representation as set by Bits 7–5 of
the AGC A Control Register. A truncation at the output of the
AGC accomplishes this task.
0x0B AGC A Hold-Off Counter
The AGC A Hold-Off counter is loaded with the value written
to this address when either a Soft_SYNC or Pin_SYNC comes
into the channel. The counter begins counting down so when it
reaches one, a SYNC is given to AGC A. This SYNC may or
may not initialize the AGC, as defined by the control word. The
AGC loop is updated with a new sample from the CIC filter
whenever a SYNC occurs. If this register is written to 1, the
AGC will be updated immediately when the SYNC occurs. If
this register is written to a 0, the AGC cannot be synchronized.
0x0C AGC A Desired Level
This 8-bit register contains the desired output power level or
desired clipping level depending on the mode of operation. This
desired Request R level can be set in dB from 0 to –23.99 in
steps of 0.094 dB. 8-bit binary floating-point representation is
used with 2-bit exponent followed by 6-bit mantissa. Mantissa is
in steps of 0.094 dB and exponent in 6.02 dB steps. For example,
10’100101 represents 2
0x0D AGC A Signal Gain
This register is used to set the initial value for a signal gain used in
the gain multiplier. This 12-bit value sets the initial signal gain
between 0 and 96.296 dB in steps of 0.024 dB. 12-bit binary
floating-point representation is used with 4-bit exponent fol-
lowed by 8-bit mantissa. For example, 0111’10001001 is
equivalent to 7
0x0E AGC A Loop Gain
This 8-bit register is used to define the open loop gain, K. Its
value can be set from 0 to 0.996 in steps of 0.0039. This value of K
is updated in the AGC loop each time the AGC is initialized.
0x0F AGC A Pole Location
This 8-bit register is used to define the open loop filter pole loca-
tion P. Its value can be set from 0 to 0.996 in steps of 0.0039.
This value of P is updated in the AGC loop each time the AGC is
initialized. This open loop pole location will directly impact the
closed loop pole locations as explained in the AGC section.
0x10 AGC A Average Samples
This 6-bit register contains the scale used for the CIC filter and
the number of power samples to be averaged before being fed to
the CIC filter.
Bits 5–2 define the scale used for the CIC filter.
Bits 1–0 define the number of samples to be averaged before
they are sent to the CIC decimating filter. This number can be
6.02 + 137
6.02 + 37
0.024 = 45.428 dB.
0.094 = 15.518 dB.
AD6634