AD6652BBC datasheet(49/76 Pages) AD

49 / 76 page

AD6652

Rev. 0 | Page 49 of 76

in the start function, the AD6652 provides four SYNC

rite the NCO frequency hold-off counter(s) (0x84) to the

he hop on pin sync bit high and the appropriate sync

enable high at External Address 4.

c logic high initiates a new

or the hold-off counter unless First Sync Only,

set. Unlike the start function, the

laced in sleep mode to achieve a

r at

a DDC channel by writing to the 0x82 and

t is advantageous to do so in the

m when the external signal on the SYNC input pin

goes high to when the NCO begins processing data is equal to

the time period set up by the NCO frequency hold-off counter

(0x84) plus five master clock cycles.

Hop with Pin Sync

Just as

pins, A, B, C, and D, which are used for very accurate channe

synchronization. Each DDC channel can be programmed to

respond to any or all four SYNC pins.

Synchronization of hop with one of the external SYNC pins is

described as follows:

appropriate value (greater than 0 and less than 2 ).

Write the NCO Frequency Register(s), 0x85 and 0x86, to

the new desired frequency.

Set t

Set the sync input select bits for each active channel. This is

done at Address 0x88:8–7. The truth table for these bits is

the same as for the start with pin sync, in Table 20.

When the selected sync pin is sampled high by the AD6652

CLK, this enables the count-down of the NCO frequency

hold-off counter. The counter is clocked with the AD6652 CL

signal. When it reaches a count of 1, the new frequency is

loaded into the NCO. Each Pin Syn

trigger event f

External Address 4:6 is set to logic high. When high, only the

first sync signal is recognized and any others are disregarded

until First Sync Only is re

channels do not need to be p

frequency hop.

Note: Each channel has a redundant pin-sync control registe

Address 0x82. This register mimics the programming as set in

External Memory Address 4:6–4. The user can control the pin

sync function of

0x88:8–7 registers, if i

application.

The time fro

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