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.
|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|
|- 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|
|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|
|- 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|
Note 1: Including POC voltage variation (2.0 to 2.2 V)
Note 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 the 78K0/Kx2, digital input for the 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.