Note: ²X² stands for don¢t care

A8~A0 : RAM address

D3~D0 : RAM data

B4~B0 : PWM 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 ex-

cept for the first command will be omitted. The source of the tone frequency and of the time

base/WDT clock frequency can be derived from an on-chip 32kHz RC oscillator, a 32.768kHz

crystal oscillator, or an external 32kHz clock. Calculation of the frequency is based on the sys-

tem frequency sources as stated above. It is recommended that the host controller should ini-

tialize the HT1647 after power-on reset, for power on reset may fail, which in turn leads to the

malfunctioning of the HT1647.

HT1647

23

April 21, 2000