AD9546SLASHPCBZ datasheet(61/205 Pages) AD

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Data Sheet

AD9546

Rev. 0 | Page 61 of 205

SYNCHRONIZATION TIME

The user programs the time associated with a forthcoming

trigger event via a 96-bit time value written to Register 0x0F0A

to Register 0x0F15. However, the user must also program

value with the primary or secondary CCS source, respectively

(see Figure 54 and Table 45 in the Inverse User Time Stamper

(IUTS) section). Then, upon issuing an IO update (via

value as the time associated with the previous synchronization

event (via the synchronization path in Figure 51).

When the device initializes, the CCS has no synchronization

event to which it can compare the first synchronization time

update. Thus, the first synchronization event following

initialization causes a synchronization error (see the

Synchronization Guard and Ready Status sections). However, a

subsequent synchronization event clears the synchronization

error and synchronizes the CCS accordingly.

There are two options for the time format: fractional seconds

and fractional nanoseconds (PTP format). Figure 52 shows the

format, the register value for the integer portion of the seconds

is the same.

For example, consider a synchronization time value of

148,264.05394857 sec. The integer seconds portion is 148,264,

which, in 48-bit hexadecimal format, is 0x 0000 0002 4328.

In fractional seconds format, the fractional portion of the

seconds entry (to the right of the virtual decimal point)

constitutes a 48-bit number with an LSB weight of 2−48 sec.

Using the same synchronization time value as in the previous

example, the fractional seconds portion is 0.05394857, which

converts to units of 2−48 sec as follows:

0.05394857 × 248 = 15,185,172,484,323.19496192

Round the result to the nearest integer, which yields

15,185,172,484,323, and convert to 48-bit hexadecimal format:

0x 0DCF 92CF D0E3.

In PTP format, the fractional portion of the seconds entry (to

the right of the virtual decimal point) constitutes a 46-bit

number (thus, the exclusion of the two fractional nanoseconds

MSBs in the bottom half of Figure 52) with an LSB weight of

2−16 ns. Using the same fractional portion value (0.05394857),

convert to units of 2−16 ns as follows:

0.05394857 × 109 × 216 = 3,535,573,483,520

This value in 46-bit hexadecimal format (rounded to the

nearest integer, if necessary) is 0x 0337 309A 0000.

0x0F15

0x0F14

0x0F13

0x0F12

0x0F11

0x0F10

0x0F0F

0x0F0E

0x0F0D

0x0F0C

0x0F0B

0x0F0A

VIRTUAL

DECIMAL POINT

MSB

LSB

SECONDS

FRACTIONAL SECONDS

0x0F15

0x0F14

0x0F13

0x0F12

0x0F11

0x0F10

0x0F0F

0x0F0E

0x0F0D

0x0F0C

0x0F0B

0x0F0A

LSB

FRACTIONAL NANOSECONDS

MSB

BITS[7:6] NOT USED

FRACTIONAL SECONDS FORMAT

FRACTIONAL NANOSECONDS FORMAT (PTP)

VIRTUAL

DECIMAL POINT

LSB

MSB

SECONDS

Figure 52. Time Formats

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