General Description
The Enhanced I/O MCUs are a series of 8-bit high performance, RISC architecture microcontrollers specifically designed for a wide range of applications. The usual Holtek microcontroller features of low power consumption, I/O flexibility, timer functions, oscillator options, power down and wake-up functions, watchdog timer and low voltage reset, combine to provide devices with a huge range of functional options while still maintaining a high level of cost effectiveness. The fully integrated system oscillator HIRC, which requires no external components and which has three frequency selections, opens up a huge range of new application possibilities for these devices, some of which may include industrial control, consumer products, household appliances subsystem controllers, etc.

FEATUREs
CPU Features
Operating voltage:
  fSYS= 4MHz: 2.2V~5.5V
  fSYS= 8MHz: 3.0V~5.5V
  fSYS= 12MHz: 4.5V~5.5V
Up to 0.33s instruction cycle with 12MHz system clock at VDD= 5V
Oscillator types:
  External high freuency Crystal -- HXT
  External RC -- ERC
  Internal high frequency RC -- HIRC
  External low frequency crystal -- LXT
Three operational modes: Normal, Slow, Sleep
Fully integrated internal 4MHz, 8MHz and 12MHz oscillator requires no external components
Watchdog Timer function
LIRC oscillator function for watchdog timer
All instructions executed in one or two instruction cycles
Table read instructions
63 powerful instructions
Up to 4-level subroutine nesting
Bit manipulation instruction
Low voltage reset function
Wide range of available package types

Peripheral Features
Up to 26 bidirectional I/O lines
Software controlled 4-SCOM lines LCD COM driver with 1/2 bias
External interrupt input shared with an I/O line
Up to two 8-bit programmable Timer/Event Counter with overflow interrupt and prescaler
Time-Base function
Programmable Frequency Divider - PFD