HT1621B详细参数：
Operating voltage : 2.4V~5.2V
Built-in 256kHz RC oscillator
External 32.768kHz crystal or 256kHz frequency source input
Selection of 1/2 or 1/3 bias, and selection of 1/2 or 1/3 or 1/4 duty LCD applications
Internal time base frequency sources
Two selectable buzzer frequencies (2kHz/4kHz)
Power down command reduces power consumption
Built-in time base generator and WDT
Time base or WDT overflow output
8 kinds of time base/WDT clock sources
32x4 LCD driver
Built-in 32x4 bit display RAM
3-wire serial
Internal LCD driving frequency source
Software configuration feature
Data mode and command mode instructions
R/W address auto increment
Three data accessing modes
VLCD pin for adjusting LCD operating voltage
HT1621: 44-pin QFP package
HT1621B: 48-pin SSOP/LQFP packages
HT1621D: 28-pin SKDIP package
HT1621G: Gold bumped chip
