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Renesas Electronics America - Knowledgebase

How to use the 78K0 and 78K0S?

Latest Updated:02/01/2008


The 78K0 and 78K0S are available as 8-bit All Flash microcontrollers. They differ in pin count, but are there any other differences, and how are they used respectively?


The 78K0/Kx2 and 78K0S/Kx1+ are both 8-bit All Flash microcontrollers, but they employ different microcontroller cores. For the differences in core, refer to A3 of "Differences among 8-bit microcontroller products (78K0/78K0S)".
In addition to pin count (and thus port count) and core differences, there are also the following functional differences.

  78K0/Kx2 78K0S/Kx1+
Operating power supply voltage 1.8 to 5.5 V 2.2Note 1 to 5.5 V
Maximum operating frequency 20 MHz 10 MHz
ROM size 8 to 128 KB (Banks are used for 64 KB and above) 1 to 8 KB
RAM size 512 bytes to 7 KB (high-speed RAM: Up to 1 KB) 128 to 256 bytes (high-speed RAM only)
16-bit timer 1 or 2 channels 0 or 1 channel
8-bit timerNote 2 4 channels 1 or 2 channels
- Carrier generation 1 channel None
Watch timer Provided in some products None
Buzzer output, clock output Provided in some products None
Watchdog timer 1 channel 1 channel
- Window function Provided (4 stages) None
- Illegal memory access detection Provided None
- Count clock Fixed to low-speed internal oscillation clock Low-speed internal oscillation clock or system clock
A/D converter (10 bits) 8 channels None or 4 channels
Serial functions    
- UART 2 channels 0 or 1 channel
- CSI 1 or 2 channels None
- CSI with automatic transmit/receive function Provided in some products None
- I2C bus 1 channel None
Key return interrupt Provided in some products None
Multiply-divide circuit Provided in some products (16x16, 32/16) Provided in some products (8x8)
POC 1.59 V or 2.7 V Fixed to 2.1 V
Internal regulator Provided None
LVI Power supply voltage/external pin Power supply voltage only
Reset pin function Reset pin Reset/input port
System clock Startup with high-speed internal oscillation clock, then selectable by program Specified in option byte
Peripheral clock System clock/high-speed internal oscillation clock Selectable as a division of system clock
Flash memory    
- Memory size specification function Provided None
- Programming with writer UART/CSI Use of X1 and X2
- Block size 1 KB 256 bytes
- Boot swap Provided None
- Mode control switching Dedicated FLMD0 pin Shared with X1
- Security function Erase and rewrite are prohibited through specification with a security command or by the programming writer. Erase and rewrite are prohibited with the protect byte.
- Self programming Startup with FLMD0 pin Startup with special sequence
Peripheral access arbitration Arbitration with waits None

Notes 1:Including POC voltage variation (2.0 to 2.2 V)

Notes 2:The supported timer functions differ.

Remark:This table lists only the main differences. For example, the source clocks that can be selected with the timer differ, the default state of the pins shared with analog input differ (analog input for 78K0/Kx2, digital input for 78K0S/Kx1+), and the various settings not listed in this table also differ.
Moreover, there are also differences in characteristics: the accuracy of the high-speed internal oscillation clock is ±5% for the 78K0/Kx2 and ±5% (±3% when the temperature is restricted) for the 78K0S/Kx1+.

Select the appropriate product taking into consideration the required peripheral functions, processing speed, program size and future product expansion.

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