AD9898 データシートの表示（PDF） - Analog Devices

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AD9898

CCD Signal Processor with Precision Timing™ Generator

Analog Devices 

AD9898

H1 AND H2 BLANKING

The AD9898 provides three options for controlling the period

where H1 and H2 pulses get blanked. These options are normal

H blanking, selective positioning for 2 H1 and H2 outputs, and

extended blanking. In all cases, HBLKMASK is used to set the

polarity of H1 during the blanking period. Table XIV describes

the registers used to control H blanking.

Normal H Blanking

For normal H blanking operation, HPULSECNT = 0 and

BLKMASK = 0 or 1. The HBLKHPOS register is not used in

this mode. Figure 23 shows one example where HBLKMASK = 0.

As seen in Figure 23, H1 and H2 are blanked while HD is Low.

Selective Positioning for Two H1 and H2 Outputs

For selective positioning operation, HPULSECNT = 1 and

HBLKMASK = 0 or 1. In this mode, two H1 pulses are output

during the blanking period. The location of these two pulses are

set using the HBLKHPOS register, as shown in Figure 24.

Extended Blanking

Extended blanking is enabled by setting HBLKEXT = 1. The

HBLKEXT register uses the 9-bit BL counter to suspend operation

of the HD and HL counters. This delays the blanking period by

the length set in the BLLEN register as shown in Figure 25.

Table XIV. H1 Blanking Registers

Register

Name

Bit

Width

Register Type

Description

HBLKMASK

1

HPULSECNT

1

HBLKEXT

1

H1BLKRETIME

1

HBLKHPOS

10

Control (0x01)

Control (0x0A)

Control (0x0A)

Control (0x03)

Sys_Reg(11)

Masking Polarity for H1 during Blanking Period1 (0 = Low, 1 = High)

H Pulse Control during Blanking Period

(0 = No Output during Blanking, 1 = Output during Blanking)

H Pulse Blanking Extend Control2

(0 = Extended Blanking Disabled, 1 = Extended Blanking Enabled)

Retimes the H1 HBLK to Internal Clock

(0 = Retiming Disabled, 1 = Retiming Enabled)

H1 Pulse ON Position during Blanking Period

NOTES

1The polarity of H2 is always the opposite polarity of the H1 polarity.

2The HBLKEXT extend control extends the blanking period by the number of counts set in the BLLEN register for the 9-bit BL counter.

HD

HBLK

(INTERNAL)

H1

HDRISE

1

H2

RG

1. THE RISING EDGE OF HBLK IS ALWAYS THE SAME AS HDRISE.

Figure 23. Normal H-Blanking Operation HBLKMASK = 0, HPULSECNT = 0, HBLKHPOS = xxx

REV. 0

–27–

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