Datasheet

AD9923A

Rev. A | Page 54 of 84

FG_TRIG OPERATION

The AD9923A contains one additional signal that can be used

in conjunction with shutter operation or general system

operation. The FG_TRIG signal is an internally generated pulse

that can be output on the SYNC pins for shutter or other system

functions. A unique feature of the FG_TRIG signal is that it is

output with respect to the MODE register field status.

The FG_TRIG signal is generated using the SHUT1 start

polarity and toggle position registers, programmable with line

and pixel resolution. The field registers for SHUT1 are ignored

because the field placement of the FG_TRIG pulse is matched

to the field count specified by the MODE register operation.

The FG_TRIGEN register contains a three-bit value that specifies

which field count contains the FG_TRIG pulse. Figure 72 shows

how the FG_TRIG pulse is generated using these registers.

After the FG_TRIG signal is specified, it can be enabled using

Bit 3 of the FG_TRIGEN register. The FG_TRIG signal is

mapped to the SYNC output if the SYNC pin is configured as

an output (SYNCENABLE = 0).

Table 41. FG_TRIG Operation Registers

SYNCENABLE 0x12 [0] 0 = configures SYNC pin as an output. By default, the FG_TRIG signal is output on the SYNC pin.

1 = SYNC pin is an external synchronization input.

FG_TRIGEN 0xF1 [3:0] [2:0] selects the field count for the pulse based on the mode field counter.

[3] = 1 to enable FG_TRIG signal output.

SHUT1POL 0x72 [1] [1] FG_TRIG start polarity.

SHUT1_ON_LN 0x74 [11:0] FG_TRIG first toggle, line location.

SHUT1_ON_PX 0x74 [25:13] FG_TRIG first toggle, pixel location.

SHUT1_OFF_LN 0x76 [11:0] FG_TRIG second toggle, line location.

SHUT1_OFF_PX 0x76 [25:13] FG_TRIG second toggle, pixel location.

FG_TRIG PROGRAMMABLE SETTINGS:

ACTIVE POLARITY.

FIRST TOGGLE POSITION, LINE AND PIXEL LOCATION.

SECOND TOGGLE POSITION, LINE AND PIXEL LOCATION.

FIELD PLACEMENT BASED ON MODE REGISTER FIELD COUNT.

MODE REGISTER

FIELD COUNT

FG_TRIG

FIELD 0 FIELD 1 FIELD 2 FIELD 0 FIELD 1

5586-070

Figure 72. FG_TRIG Signal Generation