AD9957/PCBZ Analog Devices Inc, AD9957/PCBZ Datasheet - Page 43

• Manufacturer Part Number: AD9957/PCBZ
• Description: D/A Converter Evaluation Board
• Manufacturer: Analog Devices Inc
• Series: AgileRF™r

Specifications of AD9957/PCBZ

• Silicon Manufacturer: Analog Devices
• Application Sub Type: Direct Digital Synthesizer
• Kit Application Type: Clock & Timing
• Silicon Core Number: AD9957
• Kit Contents: Board
• Main Purpose: Timing: DDS Modulators
• Embedded: No
• Utilized Ic / Part: AD9957
• Primary Attributes: 14-Bit DAC, 32-Bit Tuning Word Width
• Secondary Attributes: 1GHz, Graphical User Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The validation result latch is in a reset state whenever the sync
receiver is disabled, which forces the SYNC_SMP_ERR pin to a
Logic 0 state. To reset the validation result latch when the sync
receiver is active, however, requires the use of the Sync Timing
Validation Disable bit in the multichip sync register. To make a
setup/hold validation measurement is a two-step process. First,
write a Logic 1 to the sync timing validation disable bit. Then,
to make a measurement, write a Logic 0. The first action resets
the validation result latch and holds it in a reset state; the
second action releases the reset state and enables the validation
result latch to capture a setup/hold validation measurement.
Each time a new setup/hold validation check is desired, this
two-step procedure must be performed.
RECEIVER
SYSCLK
DELAY
LOGIC
FROM
SYNC
SYNC TIMING VALIDATION DISABLE
DELAY
DELAY
4
4
RISING EDGE
AND STROBE
SETUP AND HOLD VALIDATION
GENERATOR
Figure 58. Sync Timing Validation Block
DETECTOR
SYNC RECEIVER
4
D Q
SYNC VALIDATION
DELAY
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VALIDATION
D Q
VALIDATION
SETUP
PULSE
SYNC
HOLD
D Q
TO
CLOCK
GENERATION
LOGIC
Because the programmed value of the sync validation delay
establishes the time window for a setup/hold measurement,
the amount of delay is an important consideration for proper
operation of the validation block. The value chosen should
represent a small fraction of the SYSCLK period. For example,
if the SYSCLK frequency is 1 GHz (1000 ps period), then a
reasonable sync validation delay value is 2 (~300 ps). This
allows the validation block to ensure that the local SYSCLK
and the delayed SYNC_IN edges exhibit at least 300 ps of
timing separation. Choosing too large a value can cause the
validation block to indicate a setup/hold violation when one
does not exist. Choosing too small a value can cause the
validation block to miss a setup/hold violation when one
actually exists.
12
SYNC_SMP_ERR
AD9957