AD6634BC/PCB Analog Devices Inc, AD6634BC/PCB Datasheet - Page 38

• 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

AD6634
Hold-Off Counter hits a value of 1. If the Frequency Hold-Off
Counter is set to 1, the register will be updated as soon as the
shadow is written.
0x86: NCO Frequency Register 1
This register represents the 16 MSBs of the NCO Frequency
word. These bits are shadowed and are not updated to the regis-
ter used for the processing until the channel is either brought
out of SLEEP or a Soft_SYNC or Pin_SYNC has been issued.
In the latter two cases the register is updated only when the
Frequency Hold-Off Counter hits a value of 1. If the Frequency
Hold-Off Counter is set to 1, the register will be updated as
soon as the shadow is written.
0x87: NCO Phase Offset Register
This register represents a 16-bit phase offset to the NCO. It can
be interpreted as values ranging from 0 to just under 2 .
0x88: NCO Control Register
This 9-bit register controls features of the NCO and the channel.
The bits are defined below. For more details, the NCO section
should be consulted.
Bits 8–7 of this register choose which of the four SYNC pins are
used by the channel. The SYNC pin selected can be used to
initiate a START, HOP, or timing adjustment to the channel.
The Synchronization section provides more details on this.
Bit 6 of this register defines whether the A or B input port is
used by the channel. If this bit is low, the A Input Port is
selected; and if this bit is high, the B Input Port is selected.
Each input port consists of a 14-bit input mantissa(INx[13:0]),
a 3-bit exponent(EXPx[2:0]), and an input enable pin IENx.
The x represents either A or B.
Bits 5–4 determine how the sample clock for the channel is
derived from the high speed CLK signal. There are four pos-
sible choices. Each is defined below but for further details, the
NCO section of the data sheet should be consulted.
When these bits are 00, the input sample rate (f
channel is equal to the rate of the high speed CLK signal. When
IEN is low, the data going into the channel is masked to 0. This
SAMP
) of the
–38–
is an appropriate mode for TDD systems where the receiver
may wish to mask off the transmitted data yet still remain in the
proper phase for the next receive burst.
When these bits are 01, the input sample rate is determined by
the fraction of the rising edges of CLK on which the IEN input
is high. For example, if IEN toggles on every rising edge of
CLK, the IEN signal will only be sampled high on one out of
every two rising edges of CLK, which means that the input
sample rate f
When these bits are 10, the input sample rate is determined by
the rate at which the IEN pin toggles. The data that is captured
on the rising edge of CLK after IEN transitions from low to
high is processed. When these bits are 11, the accumulator and
sample CLK are determined by the rate at which the IEN pin
toggles. The data that is captured on the rising edge of CLK
after IEN transitions from high to low is processed. For example,
control modes 10 and 11 can be used to allow interleaved data
from either the A or B input ports and then assigned to the
respective channel. The IEN pin selects the data such that a
channel could be configured in mode 10 and another could be
configured in mode 11.
Bit 3 determines whether or not the phase accumulator of the
NCO is cleared when a Hop occurs. The Hop can originate
from either the Pin_SYNC or Soft_SYNC. When this bit is set
to 0, the Hop is phase continuous and the accumulator is not
cleared. When this bit is set to 1, the accumulator is cleared to 0
before it begins accumulating the new frequency word. This is
appropriate when multiple channels are hopping from different
frequencies to a common frequency.
Bits 2–1 control whether or not the dithers of the NCO are
activated. The use of these features is heavily determined by the
system constraints. Consult the NCO section of the data sheet
for more detailed information on the use of dither.
Bit 0 of this register allows the NCO Frequency translation stage
to be bypassed. When this occurs the data from the A Input Port is
passed down the I path of the channel and the data from the B
Input Port is passed down the Q path of the channel. This
allows a real filter to be performed on baseband I and Q data.
SAMP
will be one-half the CLK rate.
REV. 0