AD9923ABBCZ datasheet(46/88 Pages) AD

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AD9923A

Rev. 0 | Page 46 of 88

Table 37. XSUBCNT Multiplexer

Length

(Bits)

Range

Description

XSUBCNT_MUX

0 to 31

Selects internal signal to

be used for XSUBCNT

0: XV6

1: XV8

2: XV9

3: XV10

4: VSG5

5: VSG6

6: VSG7

7: VSG8

8: VSG2

9: VSG3

10: VSG4

11: VSG1

12: XV13

13: VSUB

14: MSHUT

15: STROBE

16: XV1

17: XV2

18: XV3

19: XV4

20: XV5

21: XV7

22: XV11

23: XV12

24: SHUT0

25: SHUT1

26: SHUT2

27: SHUT3

28: FG_TRIG

29: invalid setting

30: high

31: low

SUBCK: Normal Operation

By default, the AD9923A operates in a normal SUBCK configu-

ration with the SUBCK signal pulsing in every VD field (see

Figure 64). The SUBCK pulse occurs once per line, and the total

number of repetitions within the field determines the exposure

time. The SUBCK pulse polarity and toggle positions within a

line are programmable, using the SUBCKPOL and SUBCK1TOG

registers (see Table 38). The number of SUBCK pulses per field

is programmed in the SUBCKNUM register (Address 0x64).

As shown in Figure 64, the SUBCK pulses always begin in the

line following the SG active line (specified in the SGACTLINE

registers for each field). The SUBCKPOL, SUBCK1TOG,

SUBCK2TOG, SUBCKNUM, and SUBCKSUPPRESS registers

are updated at the start of the line after the sensor gate line, as

described in the Updating New Register Values section.

SUBCK: High Precision Operation

High precision shuttering is used in the same manner as normal

shuttering, but an additional register is used to control the last

SUBCK pulse. In this mode, the SUBCK pulses once per line,

but the last SUBCK in the field has an additional SUBCK pulse,

whose location is determined by the SUBCK2TOG register, as

shown in Figure 65. Finer resolution of the exposure time is

possible using this mode. Leaving the SUBCK2TOG register set

to its maximum value (0xFFFFFF) disables the last SUBCK

pulse (default setting).

SUBCK: Low Speed Operation

Normal and high precision shutter operations are used when

the exposure time is less than one field long. For exposure times

longer than one field interval, low speed shutter operation is

used. The AD9923A uses a separate exposure counter to

achieve long exposure times. The number of fields for the low

speed shutter operation is specified in the EXPOSURENUM

mode suppresses the SUBCK and VSG outputs from 0 fields up

to 4095 fields (VD periods). The VD and HD outputs can be

suppressed during the exposure period by programming the

VDHDOFF register to 1.

To generate a low speed shutter operation, trigger a long ex-

posure by writing to the TRIGGER register, Bit D3. When this

bit is set high, the AD9923A begins an exposure operation at

the next VD edge. If a value greater than 0 is specified in the

EXPOSURENUM register, the AD9923A suppresses the

SUBCK output on subsequent fields.

If the exposure is generated using the TRIGGER register and

the EXPOSURENUM register is set to 0, the behavior of the

SUBCK is the same as during normal shutter or high precision

shutter operations, in which the TRIGGER register is not used.

AD9923ABBCZ Datasheet(PDF) 46 Page - Analog Devices

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