AD9985ASLASHPCB datasheet(24/32 Pages) AD

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AD9985A

Rev. 0 | Page 24 of 32

Hsync Detect

This bit is used to indicate when activity is detected on

the Hsync input pin (Pin 30). If Hsync is held high or

low, activity will not be detected.

Table 31. Hsync Detection Results

Detect

Function

No activity detected

Activity detected

The sync processing block diagram (Figure 14) shows

where this function is implemented.

Active Hsync (AHS)

This bit indicates which Hsync input source is being

used by the PLL (Hsync input or sync-on-green).

Bit 7 and Bit 1 in this register determine which source

is used. If both Hsync and SOG are detected, the user

can determine which has priority via Bit 3 in

Bit 4 in Register 0x0E. If the override bit is set to

Logic 1, then this bit is set to the state of Bit 3 in

Table 32. Active Hsync Results

Bit 7

Bit 1

Bit 4

(Hsync

(SOG

Reg. 0x0E

Detect)

(Override)

AHS

Bit 3 in 0x0E

AHS = 0 means use the Hsync pin input for Hsync.

AHS = 1 means use the SOG pin input for Hsync.

The override bit is in Register 0x0E, Bit 4.

Detected Hsync Input Polarity Status

This bit reports the status of the Hsync input polarity

detection circuit. It can be used to determine the

polarity of the Hsync input. The detection circuit’s

location is shown in the sync processing block

diagram (Figure 14).

Table 33. Detected Hsync Input Polarity Status

Hsync Polarity Status

Result

Negative

Positive

Vsync Detect

This bit is used to indicate when activity is detected on

the Vsync input pin (Pin 31). If Vsync is held steady

high or low, activity is not detected.

Table 34. Vsync Detection Results

Detect

Result

No activity detected

Activity detected

The sync processing block diagram (Figure 14) shows

where this function is implemented.

Active Vsync (AVS)

This bit indicates which Vsync source is being used,

the Vsync input or output from the sync separator.

Bit 4 in this register determines which is active. If both

Vsync and SOG are detected, the user can determine

which has priority via Bit 0 in Register 0x0E. The user

can override this function via Bit 1 in Register 0x0E. If

the override bit is set to Logic 1, this bit is set to the

state of Bit 0 in Register 0x0E.

Table 35. Active Vsync Results

Bit 4, Reg 14H

(Vsync Detect)

Bit 1, Reg. 0x 0E

(Override)

AVS

Bit 0 in 0x0E

AVS = 0 means Vsync input.

AVS = 1 means Sync separator.

The override bit is in Register 0x0E, Bit 1.

Detected Vsync Output Polarity Status

This bit reports the status of the Vsync output polarity

detection circuit. It can be used to determine the

polarity of the Vsync output. The detection circuit’s

location is shown in the sync processing block

diagram (Figure 14).

Table 36. Detected Vsync Output Polarity Status

Vsync Polarity

Status

Result

Active low

Active high

Sync-on-Green Detect

This bit is used to indicate when sync activity is

detected on the sync-on-green input pin (Pin 49).

Table 37. Sync-on-Green Detection Results

Detect

Result

No activity detected

Activity detected

The sync processing block diagram (Figure 14) shows

where this function is implemented.

Detected Coast Polarity Status

This bit reports the status of the Coast input polarity

detection circuit. It can be used to determine the

polarity of the Coast input. The detection circuit’s

location is shown in the sync processing block

diagram (Figure 14).

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