AD9979BCPZ datasheet(24/56 Pages) AD

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AD9979

Rev. C | Page 24 of 56

MODE REGISTERS

To select the final field timing of the AD9979, use the mode

registers. Typically, all of the field and H-pattern group

information is programmed into the AD9979 at startup.

During operation, the mode registers allows the user to

select any combination of field timing to meet the current

requirements of the system. The advantage of using the mode

registers in conjunction with preprogrammed timing is that it

greatly reduces the system programming requirements during

camera operation. Only a few register writes are required when

the camera operating mode is changed, rather than having to

write in all of the vertical timing information with each camera

mode change.

A basic still camera application can require five different fields

of horizontal timing: one for draft mode operation, one for auto

focusing, and three for still-image readout. With the AD9979,

all register timing information for the five fields is loaded at

startup. Then, during camera operation, the mode registers

selects which field timing to activate depending on how the

camera is being used.

The AD9979 supports up to seven field sequences, selected

from up to 31 preprogrammed field groups, using the FIELD_SELx

registers. When FIELDNUM is greater than 1, the AD9979

starts with Field 1 and increments to each Field N at the start of

each VD.

Figure 33 provides examples of the mode configuration settings.

This example assumes having four field groups, Field Group 0

to Field Group 3, stored in memory.

Table 14. Mode Registers

Name

Length

Range

Description

HPATNUM

5 bits

0 to 31 H-pattern groups

Total number of H-pattern groups starting at Address 0x800

FIELDNUM

3 bits

0 to 7 fields

Total number of applied fields (1 = single-field operation)

FIELD_SEL1

5 bits

0 to 31 field groups

Selected first field

FIELD_SEL2

5 bits

0 to 31 field groups

Selected second field

FIELD_SEL3

5 bits

0 to 31 field groups

Selected third field

FIELD_SEL4

5 bits

0 to 31 field groups

Selected fourth field

FIELD_SEL5

5 bits

0 to 31 field groups

Selected fifth field

FIELD_SEL6

5 bits

0 to 31 field groups

Selected sixth field

FIELD_SEL7

5 bits

0 to 31 field groups

Selected seventh field

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