The M50734SP is a member of Mitsubishi's 740 Series (also written "M740") family of CMOS 8-bit single-chip microcomputers. The 740 Series is broadly 6502-compatible but with a significantly extended instruction set, additional addressing modes, on-chip peripherals, and built-in bit-manipulation instructions that make it highly suited to embedded control applications.

The "SP" suffix denotes the extended variant without on-chip program ROM — program memory is supplied externally, making it ideal for development. Production variants of the 740 family include on-chip ROM.

Register	Width	Name	Description
A	8-bit	Accumulator	Primary arithmetic and logic register. Many instructions implicitly use A.
X	8-bit	Index Register X	Indexing, loop counting, offset addressing.
Y	8-bit	Index Register Y	Indexing, loop counting, offset addressing.
SP	8-bit	Stack Pointer	Points to the top of the stack (page 1: $0100–$01FF). Decrements on push.
PC	16-bit	Program Counter	Points to the next instruction byte to be fetched.
P	8-bit	Processor Status	Condition flags — see below.

Processor Status Register (P)

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
N	V	T	B	D	I	Z	C
Negative	Overflow	T-flag (740 unique)	Break	Decimal	IRQ Disable	Zero	Carry

T flag (Bit 5) is unique to the 740 Series. When set, certain instructions operate in a special transfer mode, allowing memory-to-memory operations without disturbing the accumulator. Instructions that use the T flag are marked [T] in the instruction reference.

The M50734SP supports the following addressing modes:

Mode	Syntax	Description
Implied	INX	Operand is implied by the instruction.
Accumulator	ASL A	Operates on the accumulator.
Immediate	LDA #$42	Operand is the next byte in the instruction stream.
Zero Page	LDA $10	Single-byte address within page 0 ($0000–$00FF).
Zero Page, X	LDA $10,X	Zero page address plus X register.
Zero Page, Y	LDX $10,Y	Zero page address plus Y register.
Absolute	LDA $1234	Full 16-bit address.
Absolute, X	LDA $1234,X	16-bit address plus X register.
Absolute, Y	LDA $1234,Y	16-bit address plus Y register.
(Indirect, X)	LDA ($10,X)	Pre-indexed indirect: zero page address + X gives pointer.
(Indirect), Y	LDA ($10),Y	Post-indexed indirect: zero page pointer then add Y.
Indirect	JMP ($1234)	JMP only: 16-bit indirect pointer.
Relative	BEQ label	Signed 8-bit offset from next instruction (branch instructions).
Bit, Zero Page	SEB 3,$10	740-specific: bit number (0–7) and zero page address.
Bit, Zero Page, Relative	BBC 3,$10,label	740-specific: bit test and branch.
Special Page	JAL $F300	740-specific: special-page direct jump to $FFxx.