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78K is the trademark name of 16- and 8-bit microcontroller family[1]:23-4–23-5[2]:78 manufactured by Renesas Electronics, originally developed by NEC[3][4]:229 started in 1986.[5]:7, line 2 The basis of 78K Family is an accumulator-based register-bank CISC architecture. 78K is a single-chip microcontroller, which usually integrates; program ROM, data RAM, serial interfaces, timers, I/O ports, an A/D converter, an interrupt controller, and a CPU core, on one die.[6][7]:412

78K Family microcontrollers
ProducedFrom 1986; 33 years ago (1986) to current
Common manufacturer(s)
  • Renesas Electronics
    (formerly NEC)
Max. CPU clock rate32 kHz to 24 MHz
Instruction set78K Family
Data width16/8
Address width20(24)/16
Predecessor87AD Family,
17K Family
SuccessorRL78 Family
Variant78K0R, 78K0S, 78K0,
78K4, 78K6, 78K3,
78K1, 78K2
78K0/KX1+ board with in-circuit emulator; MINICUBE
78K0S/KA1+ Do It board
78K0R/KG3 Cool It board with in-circuit emulator; IECUBE (formerly, MINICUBE2)

Its application area is mainly simple mechanical system controls and man-machine interfaces.[8][9][10]

Regarding software development tools, C compilers and macro-assemblers are available.[11]:99 As for development tool hardware, full probing-pod type and debug port type in-circuit emulators,[12][13] and flash ROM programmers[14]:22–24 are available.

Historically, the family has 11 series with 9 instruction set architectures. As of 2018, 3 instruction set architectures, those are 8-bit 78K0, 8-bit 78K0S, and 16-/8-bit 78K0R, are still promoted for customers' new designs.[14] But in most of cases, migration to RL78 Family,[15] which is a successor of 78K0R and almost binary level compatible with 78K0R,[16]:20 is recommended.[17]



78K0 SeriesEdit

78K0 Series [de] (also known as 78K/0) is a long-running 8-bit single chip microcontroller,[18] which is the basis of 78K0S and 78K0R Series. It contains 8× 8-bit registers ×4 banks. For 16-bit calculating instructions, it performs ALU operation twice. Each instructions are performed serially without instruction pipelining. It has 16-bit 64K Byte address space.[19] Some variants of 78K0 have affordable and compact type 8-bit R-2R D/A converter, which does not have monotonicity because it is not trimmed for adjustment nor followed by operational amplifier.

In its earlier stage, the Program Memory was one-time PROM (OTP), UV-EPROM, or mask ROM.[20] But with the times, it became flash memory.[21][22]

78K0S SeriesEdit

78K0S Series (also known as 78K/0S) is a low-end version of 78K0.[23][24][25] It has 8× 8-bit registers, but without any banks. In addition, some instructions, such as multiplication and division, are removed from 78K0 instruction set architecture.[26]

78K0R SeriesEdit

78K0R Series is a 16-bit single-chip microcontroller with 3-stage instruction pipelining.[27] Its instruction set is similar to 78K0 and covers 16- and 8-bit operations. It has 20-bit 1M Byte address space.[28] 75 instructions out of 80 are identical with that of RL78 Family; its successor.[16]:20[15][29]

178K0 SeriesEdit

178K0 Series (also known as 178K/0) is a successor of NEC's 17K Family 4-bit microcontroller for DTS (Digital Tuning Systems) and remote controls.[30] It integrates 17K family's peripheral functions with the 78K0 8-bit CPU core on a chip.[31]

178K0S SeriesEdit

178K0S Series (also known as 178K/0S) is also a successor of 17K Family with the 78K0S CPU core.[32]

78K4 SeriesEdit

78K4 Series (also known as 78K/4) is a 16-bit single-chip microcontroller with 16 and 8-bit operations.[33][34][35][36] It has 16× 8-bit registers ×4 banks, which can be also used for 8× 16-bit registers ×4 banks. Some of these registers can be also used as 24-bit extension for addressing modes.[37] It has 24-bit 16M Byte address space. It has microcode-based operations named Macro Service with interrupt functions.[38]:§23.8, 560–593

78K7 SeriesEdit

78K7 Series (also known as 78K/7) is a 32-bit single-chip microcontroller with 32, 16 and 8 bit operations. It has 8× 32-bit registers ×16 banks, which can be also used for 16× 16-bit registers ×16 banks and 16× 8-bit registers ×16 banks. It has microcode-based operations named Macro Service with interrupt functions. It has 24-bit 16M Byte linear address space. It is used for some Quantum Fireball products,[39]:Photo 2 but shortly replaced with V850 Family 32-bit RISC microcontrollers.

78K6 SeriesEdit

78K6 Series (also known as 78K/6) is a 16-bit single-chip microcontroller. Its life-time was short, and less variants.

78K1 SeriesEdit

78K1 Series (also known as 78K/1) is an 8-bit single-chip microcontroller. It has 8× 8-bit registers ×4 banks. 78K1 series is targeted for servo controls of videocassette recorders. μPD78148 sub-series integrates 2 operational amplifiers.[40]

78K3 SeriesEdit

78K3 Series (also known as 78K/3) is a 16-bit single-chip microcontroller with 16 and 8 bit operations. It has 16× 8-bit ×8 banks, which can be also used for 8× 16-bit registers ×8 banks. Its address space is 16-bit 64K Byte. It is developed as high-end series of 78K Family. It has microcode-based operations named Macro Service with interrupt functions.[41]:§13.4, 261–280

This series is used for hard disk drives, especially Quantum Fireball Series.[42] μPD78364 sub-series is used for inverter compressor controls.[43] It is also used for traction control systems of some cars.

78K2 SeriesEdit

78K2 Series (also known as 78K/2) is an 8-bit single-chip microcontroller. It has 8× 8-bit registers ×4 banks. It is developed as general purpose series of 78K Family.[44]


87AD FamilyEdit

87AD Family[4]:229 is an 8-bit single-chip microcontroller. It has 8× 8-bit registers ×4 banks. Its instruction set architecture became the basis of 78K.[45]

17K FamilyEdit

17K Family[4]:229 is a 4-bit single-chip microcontroller, especially dedicated for DTS (Digital Tuning Systems) and remote controls. It has 2 plane of 128× 4-bit register files, and sophisticated fully orthogonal instruction set. This instruction set is completely different from that of 78K Family.[30]

Table list of 78K FamilyEdit

Series ALU Registers Instructions Pipeline Remark Documents
RL78-S3 16-bit 8× 8-bit ×4 banks 81 (75+6) 3-stage Successor of 78K0R [29]:8
RL78-S2 16-bit 8× 8-bit ×4 banks 75 3-stage
RL78-S1 8-bit 8× 8-bit (no bank) 74 (75-1) 3-stage
78K0R 16-bit 8× 8-bit ×4 banks 80 (75+5) 3-stage Extended 78K/0 [28]:18
78K0S 8-bit 8× 8-bit (no bank) 47 none Simplified 78K/0 [25]
78K0 8-bit 8× 8-bit ×4 banks 48 none Basic 78K/0 core [19]
178K0S 8-bit 8× 8-bit 47 none 78K/0S for DTS;
Digital Tuning System
178K0 8-bit 8× 8-bit ×4 banks 48 none 78K/0 for DTS [19][31]
78K4 16-bit 16× 8-bit ×4 banks 113 none Macro service available [37]:24, 128
78K7 32-bit 16× 16-bit ×16 banks none Macro service available [46]
78K6 16-bit Macro service available
78K1 8-bit 8× 8-bit ×4 banks 64 none For VCR servo controls [40]:3,39
78K3 16-bit 16× 8-bit ×8 banks 113–115 none Macro service available [47]:3–28, 45
78K2 8-bit 8× 8-bit ×4 banks 65 none General purpose [44]:16, 50
87AD 8-bit 8× 8-bit ×2 banks CMOS: 159
NMOS: 158
none Predecessor of 78K [45]:21, 39
(17K) 4-bit 128× 4-bit ×2 banks 47 none Predecessor of 178K [30]

See alsoEdit


  1. ^ Oklobdzija, Vojin G. (2001). The Computer Engineering Handbook. CRC Press. ISBN 9780849308857.
  2. ^ Edwards, Lewin A. R. W. (2006). So, You Wanna be an Embedded Engineer: The Guide to Embedded Engineering, from Consultancy to the Corporate Ladder. Newnes. ISBN 9780750679534.
  3. ^ "78k | The CPU Shack Museum".
  4. ^ a b c Parai, Manas Kumar; Das, Banasree; Das, Gautam (January 2013). "An Overview of Microcontroller Unit: From Proper Selection to Specific Application" (PDF). International Journal of Soft Computing and Engineering (IJSCE). 2 (6): 228–231. ISSN 2231-2307.
  5. ^ NECエレクトロニクス 8ビットマイコンのあゆみ [History of 8-bit microcontrollers of NEC Electronics] (PDF) (in Japanese). Sunhayato Corp.
  6. ^ "microcontroller". The Free Dictionary.
  7. ^ Oklobdzija, Vojin G. (2017). Digital Systems and Applications. CRC Press. ISBN 9781351838108.
  8. ^ "NEC Electronics Introduces 12 New 16-bit All Flash Microcontrollers with LCD Controller/Driver Circuit". Business Wire. 2009-01-16.
  9. ^ Garcia, Pedro Castillo; Lozano, Rogelio; Dzul, Alejandro Enrique (2006). Modelling and Control of Mini-Flying Machines. Springer Science & Business Media. ISBN 9781846281792.
  10. ^ Archived: "MPU & MCU | Renesas Electronics". 7 October 2012.
  11. ^ Emilio, Maurizio Di Paolo (2014). Embedded Systems Design for High-Speed Data Acquisition and Control. Springer. ISBN 9783319068657.
  12. ^ Electronic Specifier (2009-04-19). "NEC Electronics' new 78K Primer Kit".
  13. ^ Bender, Klaus; Jack, Peter; Koç, Ali; Péter, Istvan; Megyeri, Gergely (2001). Qualitätssicherung eingebetteter Software : Methoden und Best-Practices : [FUSIM] (in German). München: Herbert Utz Verlag. ISBN 9783831600243.
  14. ^ a b Renesas official: Renesas MPUs & MCUs 78K MCU Selection Guide. Renesas Electronics.
  15. ^ a b Dean, Alexander G.; Conrad, James M. (2012). Creating Fast, Responsive and Energy-Efficient Embedded Systems using the Renesas RL78 Microcontroller (PDF). 1290 Weston Road, Suite 306 Weston, FL 33326 USA: Micrium Press. ISBN 9781935772989.
  16. ^ a b Renesas official: Porting guide from 78K0R/FC3 to RL78/F14. Renesas Electronics.
  17. ^ "Renesas Electronics Introduces the New RL78 Microcontroller Family to Deliver Solutions for Next-Generation 8-/16-bit Embedded Applications". Renesas Electronics.
  18. ^ Hausmann, G.; Gebing, E. (1997). "The realisation of specific automotive applications with "Full" CAN functionality at "Basic" CAN cost on highly integrated 8-Bit microcontroller of NEC's 78K/0 family" (PDF). 4th International CAN Conference, ICC. 97: 4&#45, 02–11.
  19. ^ a b c Renesas official: 78K/0 Series for Instructions. Renesas Electronics.
  20. ^ Renesas official: UPD78054,78054Y Subseries User's Manual. Renesas Electronics.
  21. ^ "NEC launches 14 new 8-bit MCUs for automotive dashboard applications | EE Times". EETimes.
  22. ^ Renesas official: 78K0/Dx2 User's Manual: Hardware. Renesas Electronics.
  23. ^ Suzuki, Tetsuya (2007-06-22). Google Translate - Introduction site of: Cコンパイラで遊ぶ78K0Sマイコン [Play with the C compiler 78K0S microcomputer]. (in Japanese). Tokyo, Japan: Socym Co,.Ltd. ISBN 9784883375394.
  24. ^ Skorobogatov, Sergei (17 August 2010). Flash Memory 'Bumping' Attacks (PDF). Cryptographic Hardware and Embedded Systems, CHES 2010. Lecture Notes in Computer Science. 6225. Springer, Berlin, Heidelberg. pp. 158–172. doi:10.1007/978-3-642-15031-9_11. ISBN 9783642150319.
  25. ^ a b c Renesas official: 78K/0S Series for Instructions. Renesas Electronics.
  26. ^ Renesas official: "Difference on 78K0 and 78K0S in 8-bit All Flash microcontrollers". Renesas Electronics - Knowledgebase. 28 June 2016.
  27. ^ Kim, Dahoo; Hida, Itaru; Fukuda, Eric S.; Asai, Tetsuya; Motomura, Masato (November 2014). A Study of Transparent On-chip Instruction Cache for NV Microcontrollers. The Seventh International Conference on Advances in Circuits, Electronics and Micro-electronics. pp. 26–29. CiteSeerX ISBN 978-1-61208-379-7. ISSN 2308-426X.
  28. ^ a b Renesas official: 78K0R Microcontrollers User's Manual: Instructions. Renesas Electronics.
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  33. ^ JPRS Report: Science & technology. Japan. Foreign Broadcast Information Service. 1994. p. 25.
    The 78K/IV has upward compatibility regarding the instruction sets of the existing 78K/0, 78K/II and 78K/III. Major features of the 78K/IV are: 1) linear addressing of 16 M bytes, 2) wide operative voltage = 2.7-6.0 V, 3) efficient power management, 4) instruction sets for C compiler. NEC has developed the 1st product “puPD784026 subseries” that has upward-compatible peripheral functions of the 78K/II series.
  34. ^ Ohuchi, Mitsurou; Kawata, Kazuhide; Akiyama, Shin-ichiro; Imamura, Hirohisa; Fukushima, Kiyoshi; Ishizaki, Norihiko; Imamizu, Jun-ichi; Mori, Takehiko; Ono, Hirohihiko; Nakata, Shigeru (1994). "16ビットシングルチップマイクロコンピュ-タ78K/4シリ-ズ (半導体デバイス)" [16-Bit Single Chip Microcomputer 78K/IV Series.]. NEC Technical Journal. 47 (3): 122–127.
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  36. ^ "Micro Controller (Data Part)".
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  41. ^ Renesas official: UPD78334 User's Manual. Renesas Electronics.
  42. ^ "Software repair of hard disks HDD (Google Translate)". (in Russian). 4X_Pro.
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  47. ^ Renesas official: UPD78356 Instructions. Renesas Electrnics.

External linksEdit