WT6124 datasheet(9/39 Pages) ETC

9 / 39 page

WT6132/WT6124/WT6116

Data Sheet Rev. 1.01

Weltrend Semiconductor, Inc.

Page 10

Horizontal frequency counter

A 12-bit counter is used to measure horizontal frequency. User can choose 16ms or 32ms time interval

to count pulse number of Hsync every 16.384ms or 32.768ms. For example, if QUICK bit is set, when a

16.384ms time frame begins, it resets the counter and starts counting Hsync pulses till 16ms reached,

then loads the counter value to HFREQ_H and HFREQ_L registers. If the H frequency is over 125KHz,

the H counter will stop counting and set overflow flag (HOVF ) to “1”.

The sync processor interrupt is generated every 16.384ms or 32.768ms for checking H frequency. This

interrupt will be cleared after reading the HFREQ_H register.

Fig.5 Horizontal Frequency Counter timing

Horizontal Frequency Register

Name

Addr R/W Initial

Bit 7

Bit 6

Bit 5

Bit4

Bit 3

Bit 2

Bit 1

Bit 0

HFREQ_L 0008h

xxh

HLVL

HINPOL

HFL4

HFL3

HFL2

HFL1

HFL0

HFREQ_H 0009h

xxh

HOVF

HFH6

HFH5

HFH4

HFH3

HFH2

HFH1

HFH0

Bit Name

Description

HLVL

“1” : Indicates Hsync pin is high level.

“0” : Indicates Hsync pin is low level.

HINPOL

“1” : Indicates Hsync input is positive polarity.

“0” : Indicates Hsync input is negative polarity.

HOVF

Indicates H counter is overflowed (over 125KHz) when this bit is set.

HFH6 …HFH0 Indicates the Hsync frequency in kHz.

HFL4 … HFL0 When QUICK=”0”, HFL4 ~ HFL0 indicates the Hsync frequency in 31.25Hz unit.

When QUICK=”1”, HFL4 ~ HFL1 indicates the Hsync frequency in 62.5Hz.

Example of Hsync Frequency Calculation

QUICK=”1”

QUICK=”0”

HFH6..0

HFL4..0

Max. Freq

Min. Freq

HFH6..0

HFL4..0

Max. Freq

Min. Freq

$40h

$00000b

64.0313KHz 63.9687KHz

$40h

$0000xb

64.0625KHz 63.9375KHz

$40h

$00001b

64.0625KHz 64.0000KHz

$40h

$00010b

64.0938KHz 64.0312KHz

$40h

$0001xb

64.1250KHz 64.0000KHz

$40h

$00011b

64.1250KHz 64.0625KHz

$51h

$10000b

81.5313KHz 81.4687KHz

$51h

$1000xb

81.5625KHz 81.4375KHz

$51h

$10001b

81.5625KHz 81.5000KHz

$51h

$10010b

81.5938KHz 81.5312KHz

$51h

$1001xb

81.6250KHz 81.5000KHz

$51h

$10011b

81.6250KHz 81.5625KHz

Hfreq Counter

Enable

16.384/32.768

16/32 ms

Hsync

Hfreq Counter

Clock

Interrupt

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