Datasheet
General-Purpose Register
Program Counter
Stack Pointer
Status Register
Constant Generator
General-Purpose Register
General-Purpose Register
General-Purpose Register
PC/R0
SP/R1
SR/CG1/R2
CG2/R3
R4
R5
R12
R13
General-Purpose Register
General-Purpose Register
R6
R7
General-Purpose Register
General-Purpose Register
R8
R9
General-Purpose Register
General-Purpose Register
R10
R11
General-Purpose Register
General-Purpose Register
R14
R15
MSP430FW429, MSP430FW428
MSP430FW427, MSP430FW425, MSP430FW423
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SLAS383E –OCTOBER 2003–REVISED DECEMBER 2013
Short-Form Description
CPU
The MSP430 CPU has a 16-bit RISC architecture
that is highly transparent to the application. All
operations, other than program-flow instructions, are
performed as register operations in conjunction with
seven addressing modes for source operand and four
addressing modes for destination operand.
The CPU is integrated with 16 registers that provide
reduced instruction execution time. The register-to-
register operation execution time is one cycle of the
CPU clock.
Four of the registers, R0 to R3, are dedicated as
program counter, stack pointer, status register, and
constant generator, respectively. The remaining
registers are general-purpose registers.
Peripherals are connected to the CPU using data,
address, and control buses, and can be handled with
all instructions.
Instruction Set
The instruction set consists of the original 51
instructions with three formats and seven address
modes. Each instruction can operate on word and
byte data. Table 2 shows examples of the three types
of instruction formats; Table 3 shows the address
modes.
Table 2. Instruction Word Formats
INSTRUCTION FORMAT EXAMPLE OPERATION
Dual operands, source-destination ADD R4,R5 R4 + R5 → R5
Single operands, destination only CALL R8 PC→(TOS), R8 →PC
Relative jump, un/conditional JNE Jump-on-equal bit = 0
Table 3. Address Mode Descriptions
ADDRESS MODE S
(1)
D
(1)
SYNTAX EXAMPLE OPERATION
Register ● ● MOV Rs, Rd MOV R10, R11 R10 → R11
Indexed ● ● MOV X(Rn), Y(Rm) MOV 2(R5), 6(R6) M(2+R5)→ M(6+R6)
Symbolic (PC relative) ● ● MOV EDE, TONI M(EDE) → M(TONI)
Absolute ● ● MOV & MEM, & TCDAT M(MEM) → M(TCDAT)
Indirect ● MOV @Rn, Y(Rm) MOV @R10, Tab(R6) M(R10) → M(Tab+R6)
M(R10) → R11
Indirect autoincrement ● MOV @Rn+, Rm MOV @R10+, R11
R10 + 2→ R10
Immediate ● MOV #X, TONI MOV #45, TONI #45 → M(TONI)
(1) S = source D = destination
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