HT1621

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10

Application Circuits

Host Controller with an HT1621 Display System

Note: The connection of

and

pin can be selected depending on the requirement of the MCU.

Adjust R (external pull-high resistance) to fit user’s time base clock.

In order to obtain the correct frequency, two additional load capacities (C1,C2) are needed. The value of the capacity depends

on how accurate the crystal is. We suggest that you can follow the table, which suggests the value of capacities.

The table illustrations the suggestion value of capacities (C1,C2)

Crystal Error

Capacity Value

±10ppm

0

~10p

10

~20ppm

10

~20p

Command Summary

Name

ID

Command Code

D/C

Function

Def.

READ

110

A5A4A3A2A1A0D0D1D2D3

D

Read data from the RAM

WRITE

101

A5A4A3A2A1A0D0D1D2D3

D

Write data to the RAM

READ-MODIFY-

WRITE

101

A5A4A3A2A1A0D0D1D2D3

D

READ and WRITE to the RAM

SYS DIS

100

0000-0000-X

C

Turn off both system oscillator and LCD

Bias generator

Yes

SYS EN

100

0000-0001-X

C

Turn on system oscillator

LCD OFF

100

0000-0010-X

C

Turn off LCD bias generator

Yes

LCD ON

100

0000-0011-X

C

Turn on LCD bias generator

TIMER DIS

100

0000-0100-X

C

Disable time base output

WDT DIS

100

0000-0101-X

C

Disable WDT time-out flag output

TIMER EN

100

0000-0110-X

C

Enable time base output

WDT EN

100

0000-0111-X

C

Enable WDT time-out flag output