Decrypt Chip HOLTEK HT48R50A-1 I/O Type 8-Bit MCU

We can decrypt chip HOLTEK HT48R50A-1 I/O Type 8-Bit MCU, please view the IC Chip features for your reference:



  • · Operating voltage:

fSYS=4MHz: 2.2V~5.5V

fSYS=8MHz: 3.3V~5.5V

  • · Low voltage reset function
  • · 35 bidirectional I/O lines (max.)
  • · 1 interrupt input shared with an I/O line
  • · 8-bit programmable timer/event counter with overflow

interrupt and 8-stage prescaler

flow interrupts

  • · On-chip RC oscillator, external crystal and RC oscil-


  • · 32768Hz crystal oscillator for timing purposes only
  • · Watchdog Timer

General Description

The HT48R50A-1/HT48C50-1 are 8-bit high perfor-

mance, RISC architecture microcontroller devices spe-

cifically designed for multiple I/O control product

applications. The mask version HT48C50-1 is fully pin

and functionally compatible with the OTP version

HT48R50A-1 device.


  • · 4096´15 program memory ROM
  • · 160´8 data memory RAM
  • · Buzzer driving pair and PFD supported
  • · HALT function and wake-up feature reduce power


  • · 6-level subroutine nesting
  • · Up to 0.5ms instruction cycle with 8MHz system clock

at VDD=5V

The advantages of low power consumption, I/O flexibil-

ity, timer functions, oscillator options, HALT and

wake-up functions, watchdog timer, buzzer driver, as

well as low cost, enhance the versatility of these devices

to suit a wide range of application possibilities such as

industrial control, consumer products, subsystem con-

trollers, etc.

Functional Description

Execution Flow

The system clock for the microcontroller is derived from

either a crystal or an RC oscillator. The system clock is

internally divided into four non-overlapping clocks. One

instruction cycle consists of four system clock cycles.

Instruction fetching and execution are pipelined in such

a way that a fetch takes an instruction cycle while de-

coding and execution takes the next instruction cycle.

However, the pipelining scheme causes each instruc-

tion to effectively execute in a cycle. If an instruction

changes the program counter, two cycles are required to

complete the instruction.

Program Counter PC

The program counter (PC) controls the sequence in

which the instructions stored in the program ROM are

executed and its contents specify a full range of pro-

gram memory.

After accessing a program memory word to fetch an in-

struction code, the contents of the program counter are

incremented by one. The program counter then points to

the memory word containing the next instruction code.

When executing a jump instruction, conditional skip ex-

ecution, loading PCL register, subroutine call, initial re-

set, internal interrupt, external interrupt or return from

subroutine, the PC manipulates the program transfer by

loading the address corresponding to each instruction.

The conditional skip is activated by instructions. Once

the condition is met, the next instruction, fetched during

the current instruction execution, is discarded and a

dummy cycle replaces it to get the proper instruction.

Otherwise proceed with the next instruction.

The lower byte of the program counter (PCL) is a read-

able and writeable register (06H). Moving data into the

PCL performs a short jump. The destination will be

within 256 locations.

When a control transfer takes place, an additional

dummy cycle is required.

Program Memory ROM

The program memory is used to store the program in-

structions which are to be executed. It also contains

data, table, and interrupt entries, and is organized into

4096´15 bits, addressed by the program counter and ta-

ble pointer.

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