Mitsubishi 740

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The Mitsubishi 740, also known as MELPS 740, was a series of 8-bit CMOS microcontrollers and microprocessors with an enhanced MOS Technology 6502 compatible core. The ICs were manufactured by Mitsubishi Electric during the 1980s and 1990s.[1]


In 1984, the first 740-series part, M50740, appeared in the 1984 Mitsubishi Single-Chip Microcontroller Databook,[2] and was manufactured by Mitsubishi Electric. Further research is needed to determine the exact date the M50740 was announced.

In 1998, it was reported in EDN magazine, that MELPS 740 family had more than 600 different variations.[3]

In 2002, Mitsubishi Electric and Hitachi agreed to merge their chip operations into a new $7 billion semiconductor company to be called Renesas Technology. The companies said they would both move their respective semiconductor operations into Renesas, including microcomputer, logic, analog, discrete devices, and memory (flash memory, SRAM, etc.) with the exception of DRAMs.[4] Renesas Technology was established on April 1, 2003, as a joint venture of Hitachi (55%) and Mitsubishi Electric (45%).

In 2009, Renesas Technology and NEC Electronics reached a basic agreement to merge, and on April 1, 2010 the two merged into Renesas Electronics.

Though legacy Mitsubishi parts are no longer manufactured, the 740 instruction set is still alive in newer Renesas microcontroller series, such as 38000/740 series and 7200 series.

Instruction Set[edit]

The Mitsubishi 740 family has a processor core that executes a superset of the 6502 instruction set. There is a core set of new instructions common across all 740 family members, plus other instructions that exist in specific parts.[1]

Common Instructions

The following is a list of new instructions and existing instructions with new modes in all 740 family parts.[1]

  • BBC - Branch Bits Clear - Branches when the contents of the bit specified in the accumulator or memory are clear (0).
  • BBS - Branch Bits Set - Branches when the contents of the bit specified in the accumulator or memory are set (1).
  • BRA - Branch Always - Jump to address where offset has been added to the program counter.
  • CLB - Clear Bits - Clear the contents of the bit specified in the accumulator or memory to zero (0).
  • CLT - Clear T Flag - Clear the contents of X-modified arithmetic mode flag to zero (0).
  • COM - Complement - One's complement (1's) of contents of memory and store it into memory.
  • DEC - Decrement - Decrement the contents of accumulator or memory by one (1).
  • INC - Increment - Increment the contents of accumulator or memory by one (1).
  • JMP - Jump Absolute - Jump to new address.
  • JSR - Jump Subroutine - Store contents of program counter in stack, then jump to new address.
  • LDM - Load Memory - Load memory with immediate value.
  • RRF - Rotate Right 4 - Rotate the contents of memory to the right by 4 bits.
  • SEB - Set Bits - Set the specified bit contents of accumulator or memory to one (1).
  • SET - Set T flag - Set the contents of X-modified arithmetic mode floag to one (1).
  • TST - Test - Tests whether the contents of memory are zero (0) or not.
Multiply/Divide instructions

The following instructions are available in M37450 parts.[1]

  • MUL ($62) - Multiply 8-bit x 8-bit - Multiplies accumulator with the memory specified by the zero page X addressing mode and stores the high byte of the result on the stack and the low byte in the accumulator.
  • DIV ($E2) - Divide 16-bit / 8-bit - Divides by accumulator the 16-bit data that is the contents of M(zz+x+1) for high byte and the contents of the next address memory for low byte, and stores the quotient in the accumulator and the remainder on the stack as one's complement.
Oscillator instructions

The following instructions are available in M50740A, M50740ASP, M50741, M50752, M50757, M50758 parts.[1]

  • SLW ($C2) - Releases the connection between the oscillator output and pin Xoutf.
  • FST ($E2) - Connects oscillator output to Xoutf.

The following instructions are not available in M50740A, M50740ASP, M50741, M50752, M50757, M50758 parts.[1]

  • WIT ($C2) - Stops the internal clock.

The following instructions are not available in M50752, M50757, M50758 parts.[1]

  • STP ($42) - Stops the oscillation of the oscillator.

Part groups[edit]

Mitsubishi M50734SP-10 and M50747 microcontrollers
Parts with external EPROM / ROM

These parts don't have any internal EEPROM or ROM, thus require an external EEPROM or ROM to hold the firmware.[1]

Parts with external piggyback-EPROM

These parts have pins on the top of the package to allow an EPROM to be plugged into it. These parts are expensive and primarily used during development purposes.[1]

  • M37450PSS, M37450PFS.
  • M50740-PGYS, M50742-PGYS, M50743-PGYS, M50745-PGYS, M50752-PGYS, M50753-PGYS.
  • M50931-PGYS, M50941-PGYS, M50950-PGYS, M50955-PGYS, M50964-PGYS.
Parts with internal EPROM

These parts have internal EPROM memory. They are available as either as OTP (one-time programmable) EPROM or Eraseable Window EPROM.[1]

  • M37410E, M37450E.
  • M50746E, M50747E.
  • M50944E, M50957E, M50963E.
Parts with internal Mask-ROM

Commercial temperature:[1]

  • M37410M, M37415M, M37450M.
  • M50708, M50740, M50740A, M50741, M50742, M50743, M50744, M50745, M50746, M50747, M50747H, M50752, M50753, M50754, M50757, M50758.
  • M50930, M50931, M50932, M50940, M50941, M50943, M50944, M50950, M50951, M50954, M50955, M50957, M50959, M50963, M50964.

Extended temperature:[1]

  • M50744T, M50747T, M50753T.
  • M50930T.



The M50734 is a ROM/RAM-less device includes peripherals such as UART, Serial I/O, A/D, Watchdog timer, VCU, 32 parallel I/O ports. A choice of 8 and 16-bit timers to manage real time tasks. It's instruction set is a superset of the 6502 microprocessor.[1]

Incorporated into this particular IC are the following:[1]

The M50734SP/FP and the M50734SP/FP-10 are unique CMOS LSI microprocessor with UART, clocked serial I/O, A-D converter, VCU, watchdog timer and 32-bit parallel I/O arranged around the M5040 CPU core. Since the M50734 has multiple internal timers for real-time control, it is ideal for controlling office automation equipment such as printers, typewriters, plotters, copy machines, FAX and handy word processors. Use of the CMOS process enables low power consumption, making the M50734SP also suitable for applications where battery-powered operation is required.

The difference between the M50734SP and the M50734FP, or between the M50734SP-10 and the M50734FP-10 lies only in the package. The difference between the M50734SP/FP and the M50734SP/FP-10 lies only in the maximum clock frequency.

Other vendors[edit]

In the 1990s a clone of the M50959 was manufactured in Russia with the designation KF1869VE1 (Russian: КФ1869ВЕ1).[5]

See also[edit]


External links[edit]

3rd party