AD9923ABBCZ datasheet(50/88 Pages) AD

50 / 88 page

AD9923A

Rev. 0 | Page 50 of 88

SHUT Signal Operation

SHUT signal operation is shown in Figure 68 through Figure 71.

Table 39 shows the register parameters for controlling the

SHUT signals. There are three different ways to use the SHUT

signals: automatic trigger, single trigger, and manual control.

Automatic Trigger

Generally, SHUT signals are triggered together with an expo-

sure or readout operation, using the TRIGGER register. The

SHUT_ON and SHUT_OFF positions are fully programmable

to anywhere within the exposure period, using the field

(SHUT_ON_FD/SHUT_OFF_FD), line

(SHUT_ON_LN/SHUT_OFF_LN), and pixel

(SHUT_ON_PX/SHUT_OFF_PX) registers.

The field registers define the field in which the line and pixel

values are used, with respect to the value of the exposure counter.

The on and off positions can occur as soon as the field contains

the last SUBCK (Exposure Field 0), or as late as the final exposure

field before the readout begins. Separate field registers allow the

on and off positions to occur in different exposure fields.

Single Trigger

SHUT signals can be triggered without triggering an exposure

or readout operation. In this case, SHUT signals are triggered

using the TRIGGER register, but the exposure bit is not triggered.

Both the SHUT on and off positions occur in the next field, and

the SHUT_ON_FD/SHUT_OFF_FD register values are ignored.

Single trigger operation is useful if a pulse is required immedi-

ately in the next field without the occurrence of an exposure or

readout operation. Also, single trigger operation is useful when

the exposure or readout operation is manually generated without

using the TRIGGER register, and the SUBCK and VSG masking

are manually controlled.

Note that single trigger operation cannot occur if an exposure

operation has been triggered. SHUT signals behave in automatic

trigger mode if they, and an exposure operation, have been

triggered.

Manual Control

Any SHUT signal can be controlled in manual control mode,

instead of using the TRIGGER register to activate it. In this

mode, the individual on and off lines and pixel positions are

used separately, depending on the status of the manual signal

control register. Note that only a single toggle position, either

off or on, can be used in a VD interval.

As with single trigger operation, when manual control is

enabled, the SHUT_ON_FD/SHUT_OFF_FD register values

are ignored.

Because there is a separate bit to enable manual control on

SHUT signals, this operation can be used regardless of the

status of a triggered exposure operation.

Note that manual control can be used in conjunction with

automatic or single trigger operations. If a SHUT signal is turned

on using manual control, and then manual control is disabled,

the SHUT signal remains on. If a subsequent trigger operation

occurs, the on position toggle is ignored, because the signal is

already on. In this case, only the off position can be triggered.

SUBCK

VSUB OPERATION:

1ACTIVE POLARITY IS DEFINED BY VSUBPOL (ABOVE EXAMPLE IS VSUB ACTIVE HIGH).

2ON POSITION IS PROGRAMMABLE, MODE 0 TURNS ON AT THE START OF EXPOSURE, MODE 1 TURNS ON AT THE START OF READOUT.

3OFF POSITION OCCURS AT END OF READOUT.

4OPTIONAL VSUB KEEP-ON MODE LEAVES THE VSUB ACTIVE AT THE END OF THE READOUT.

VSG1

VSUB

MODE 0

MODE 1

TRIGGER

VSUB

tEXP

READOUT

Figure 67. VSUB0, VSUB1 Signal Programmability

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