AD9546SLASHPCBZ datasheet(194/205 Pages) AD

194 / 205 page

AD9546

Data Sheet

Rev. 0 | Page 194 of 205

TIME STAMP MEASUREMENT

The AD9546 is particularly well suited for applications

requiring the measurement of clock frequencies and clock

timing offsets. Measurement of frequency and time offset is

made possible by digitizing (time stamping) input clock edges

using TDCs. Each of the four primary reference inputs (REFA,

REFAA, REFB, REFBB) and four auxiliary reference inputs

(auxiliary REF0, auxiliary REF1, auxiliary REF2, and auxiliary

REF3) of the AD9546 has a dedicated TDC (see Figure 130).

The AD9546 embodies a user time stamp capturing system that

gives the user access to time stamps generated by the TDCs (see

the User Time Stamper (UTS) section). The UTS system

embodies nine time stamp capturing units (UTS 0 to UTS 8),

making it possible to capture time stamps from all eight input

time stamp sources (REFx and auxiliary REFx) concurrently.

The UTS system stores captured time stamps in the UTS FIFO,

which the user accesses via the serial port (see the UTS

Readback FIFO section). The FIFO has limited capacity, which

means if the time stamp arrival rate to the FIFO exceeds the

FIFO extraction rate (on average), the FIFO eventually

overflows. Because a FIFO overflow causes the FIFO to stop

accepting time stamps from the UTSs, the user must extract the

FIFO contents at an average rate that exceeds the average time

stamp arrival rate to the FIFO (otherwise, time stamps are lost).

Thus, the serial port read rate puts an upper limit on the time

stamp arrival rate to the FIFO.

REFA

TDC

REFAA

TDC

REFB

TDC

REFBB

TDC

Mx PIN

MATRIX

AUX REF0

AUX REF1

AUX REF2

AUX REF3

TDC

SDO/M5

CSB/M6

DIGITAL CROSS

POINT MUX

UTS 0

UTS

FIFO

SERIAL

PORT

SPI/I2C

AD9546

TIME

STAMPS

CONTROLLER

UTS 1

UTS 2

UTS 3

UTS 4

UTS 5

UTS 6

UTS 7

UTS 8

TIME

STAMPS

UP TO 8

CLOCK INPUTS

Figure 130. Time Stamp Measurement Application

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