Name

ID

Command Code

D/C

Function

Def.

F32

100 101X-0101-X

C

Time base clock output: 32Hz

The WDT time-out flag after: 1/8 s

F64

100 101X-0110-X

C

Time base clock output: 64Hz

The WDT time-out flag after: 1/16 s

F128

100 101X-0111-X

C

Time base clock output: 128Hz

The WDT time-out flag after: 1/32 s Yes

TEST

100 1110-0000-X

C

Test mode, user don¢t use.

NORMAL

100 1110-0011-X

C

Normal mode

Yes

Note: X : Don¢t care

A7~A0 : RAM address

D3~D0 : RAM data

D/C : Data/Command mode

Def. : Power on reset default

All the bold forms, namely 110, 101, and 100, are mode commands. Of these, 100 indicates the

command mode ID. If successive commands have been issued, the command mode ID except for the

first command will be omitted. The source of the tone frequency and of the time base/WDT clock fre-

quency can be derived from a 32.768kHz crystal oscillator or an external 32kHz clock. Calculation of

the frequency is based on the system frequency sources as stated above. It is recommended that the

host controller should initialize the HT16270 after power on reset, for power on reset may fail, which

in turn leads to malfunctioning of the HT16270.

HT16270

16

April 21, 2000