8-bit General Purpose Ultra-Low-End Market KA MCUs

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Block Diagram

S08KA Microcontroller Block Diagram

S08KA Microcontroller Block Diagram


8-bit RS08 Central Processor Unit (CPU)

  • Up to 10 MHz (bus frequency) RS08 CPU at 1.8 volts for 100 ns minimum instruction time
  • Subset of HC08 instruction set with added BGND instruction
  • Supports tiny/short address mode
  • Index addressing scheme through memory mapped registers X and D[X] within the tiny address range
  • 14 byte code-efficient RAM
  • X and D[X] mapped within code-efficient tiny address space
  • 16 byte code-efficient peripheral register space
  • Page window
  • Simplified interrupt mechanism
  • Subroutine call/return mechanism

Integrated Third-Generation Flash

  • Fast, byte-writable programming— up to 20 µs/byte
  • Offers 1 KB write/erase cycles minimum over temperature

Flexible Clock Options

  • Internal clock source module containing a frequency-locked loop (FLL) controlled by internal or external reference
  • Precision trimming of internal reference allows typical 0.2 percent resolution and +1 percent to -1 percent deviation over operating temperature and voltage
  • Internal reference clock can be trimmed from 31.25 kHz to 39.065 kHz, allowing for maxim 10 MHz Bus frequency output


  • 2 x 8-bit modulo timer with 8-bit prescaler
  • 2-ch., 16-bit timer/PWM
  • Allows external timer clock source


  • 12-ch., 10-bit resolution
  • 2.5 µs conversion time; automatic compare function
  • Trigger conversion using RTI counter

Analog Comparator

  • Option to compare to internal reference
  • Option to route comparator output directly to pin
  • Allows operation in MCU STOP mode


  • Inter-integrated circuit bus module capable of operation up to 100 kbps with maximum bus loading

Real-Time Interrupt

  • Real-time interrupt trigger with 3-bit prescaler
  • Built-in low-power 1 kHz clock source

Up to 18 GPIOs

  • Software selectable pull-ups on ports when used as input (internal pull-up on RESET)
  • Software selectable slew rate control on ports when used on output
  • 8-pin keyboard interrupt module with software selectable polarity on edge or edge/level modes

System Protection

  • Watchdog computer operating properly (COP) reset with option to run from dedicated 1 kHz internal clock source or bus clock
  • Low voltage detection with reset or interrupt
  • Illegal opcode and illegal address detection with reset
  • Security feature for flash

Background Debugging System

  • On-chip BDM


  • Pin-compatible with SH, QG family

Complementary Products

RS08KA Family Members

Features RS08KA1 RS08KA2 RS08KA4 RS08KA8
BUS Speed (MHz) 10 10 10 10
FLASH (KBytes) 1 2 4 8
RAM (Bytes) 63 63 126 254
GPIO 2 / 4 2 / 4 14 / 18 14 / 18
Keyboard Interrupt 3 / 5 3 / 5 8 8
ADC Channels None None 12 12
ADCMP Module Yes Yes Yes Yes
Serial Comunications None None I2C I2C
MTIM Module Yes Yes Yes Yes
Timers None None One Timer One Timer
Package 6-pin DFN
6-pin DFN


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