AD9540/PCBZ Analog Devices Inc, AD9540/PCBZ Datasheet - Page 27

• Manufacturer Part Number: AD9540/PCBZ
• Description: 650 MHz Clock Generator Eval Bd.
• Manufacturer: Analog Devices Inc

Specifications of AD9540/PCBZ

• Main Purpose: Timing, Clock Generator
• Utilized Ic / Part: AD9540
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

CONTROL REGISTER BIT DESCRIPTIONS
Control Function Register 1 (CFR1)
This control register is comprised of four bytes that must be
written during a write operation involving CFR1. CFR1 is used
to control various functions, features, and operating modes of
the AD9540. The functionality of each bit is described below. In
general, the bit is named for the function it serves when the bit
is set.
CFR1[31:25] Open
Unused locations. Write a Logic 0.
CFR1[24] STATUS_Error (Read Only)
When the device is operating in automatic synchronization
mode or hardware manual synchronization mode the
SYNC_IN/STATUS pin behaves as the SYNC_IN. To determine
whether or not the PLL has become unlocked while in
synchronization mode, this bit serves as a flag to indicate that
an unlocked condition has occurred within the phase frequency
detector. Once set, the flag stays high until it is cleared by a
readback of the value even though the loop might have
relocked. Readback of the CFR1 register clears this bit.
CFR1[24] = 0 indicates that the loop has maintained lock since
the last readback.
CFR1[24] = 1 indicates that the loop became unlocked at some
point since the last readback of this bit.
CFR1[23] Load Sweep Ramp Rate at I/O_UPDATE, also
known as Load SRR @ I/O_UPDATE
The sweep ramp rate is set by entering a value to a down-
counter that is clocked by the SYNC_CLK. Each time a new
step is taken in the linear sweep algorithm, the ramp rate value
is passed from the linear sweep ramp rate register to this down-
counter. When set, CFR1[23] enables the user to force the part
to restart the countdown sequence for the current linear sweep
step by toggling the I/O_UPDATE pin.
CFR1[23] = 0 (default). The linear sweep ramp rate countdown
value is loaded only upon completion of a countdown sequence.
CFR1[23] = 1. The linear sweep ramp rate countdown value is
reloaded, if an I/O_UPDATE signal is sent to the part during a
sweep.
CFR1[22] Auto-Clear Frequency Accumulator
This bit enables the auto clear function for the frequency
accumulator. The auto clear function serves as a clear and release
function for the frequency accumulator. This performs the linear
sweep operation that then begins sweeping from a known value of
FTW0.
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CFR1[22] = 0 (default). Issuing an I/O_UPDATE has no effect
on the current state of the frequency accumulator.
CFR1[22] = 1. Issuing an I/O_UPDATE signal to the part clears
the current contents of the frequency accumulator for one sync-
clock period.
CFR1[21] Auto Clear Phase Accumulator
This bit enables the auto clear function for the phase
accumulator. The auto clear function serves as a reset function
for the phase accumulator, which then begins accumulating from
a known phase value of 0.
CFR1[21] = 0 (default). Issuing an I/O_UPDATE has no effect
on the current state of the phase accumulator.
CFR1[21] = 1. Issuing an I/O_UPDATE clears the current
contents of the phase accumulator for one SYNC_CLK period.
CFR1[20] Enable Sine Output
Two different trigonometric functions can be used to convert
the phase angle to an amplitude value, cosine, or sine. This bit
selects the function used.
CFR1[20] = 0 (default). The phase-to-amplitude conversion
block uses a cosine function.
CFR1[20] = 1. The phase-to-amplitude conversion block uses a
sine function.
CFR1[19] Clear Frequency Accumulator
This bit serves as a static clear, or a clear-and-hold bit for the
frequency accumulator. It prevents the frequency accumulator
from incrementing the value as long as it is set.
CFR1[19] = 0 (default). The frequency accumulator operates
normally.
CFR1[19] = 1. The frequency accumulator is cleared and held at 0.
CFR1[18] Clear Phase Accumulator
This bit serves as a static clear, or a clear-and-hold bit for the
phase accumulator. It prevents the phase accumulator from
incrementing the value as long as it is set.
CFR1[18] = 0 (default). The phase accumulator operates normally.
CFR1[18] = 1. The phase accumulator is cleared and held at 0.
CFR1[17:16] Open
Unused locations. Write a Logic 0.
CFR1[15] LSB First Serial Data Mode
The serial data transfer to the device can be either MSB first or
LSB first. This bit controls that operation.
AD9540