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Addressing modes

The MSP430 supports seven addressing modes for the source operand and four addressing modes for the destination operand (see bellow). The following sections describe each of the addressing modes, with a brief description, an example and the number of CPU clock cycles required for an instruction, depending on the instruction format and the addressing modes used.

Mode Source operand Destination operand Description
Register mode X X Single cycle
Indexed mode X X Table processing
Symbolic mode X X Easy to read code, PC relative
Absolute mode X X Directly access any memory location
Indirect register mode X Access memory with pointers
Indirect auto increment mode X Table processing
Immediate mode X Unrestricted constant values

Before describing the addressing modes, it is important to mention the clock cycles required by interrupts and resets.

Action Cycles Length (words)
Return from interrupt 5 1
Interrupt accepted 6 -
Watchdog timer reset 4 -
Hard reset 4 -

Register mode

Register mode operations work directly on the processor registers, R4 through R15, or on special function registers, such as the program counter or status register. They are very efficient in terms of both instruction speed and code space.

Description: Register contents are operands.

Source mode bits: As = 00 (source register defined in the opcode).

Destination mode bit: Ad=0 (destination register defined in the opcode).

Syntax: Rn.

Length: One or two words.

Comment: Valid for source and destination.

Example 1: Move (copy) the contents of source (register R4) to destination (register R5). Register R4 is not affected.

Before operation: R4=A002h R5=F50Ah PC = PC pos

Operation: MOV R4, R5

After operation: R4=A002h R5=A002h PC = PC pos + 2

The first operand is in register mode and depending on the second operand mode, the cycles required to complete an instruction will differ. The next table shows the cycles required to complete an instruction, depending on the second operand mode.

Operands 2 nd operand mode Operator Cycles Length (words)
2 Register Any 1* 1
2 Indexed, Symbolic or Absolute Any 4 2
1 N/A RRA, RRC, SWPB or SXT 1 1
1 N/A PUSH 3 1
1 N/A CALL 4 1

Indexed mode

The Indexed mode commands are formatted as X(Rn), where X is a constant and Rn is one of the CPU registers. The absolute memory location X+Rn is addressed. Indexed mode addressing is useful for applications such as lookup tables.

Description: (Rn + X) points to the operand. X is stored in the next word.

Source mode bits: As = 01 (memory location is defined by the word immediately following the opcode).

Destination mode bit: Ad=1 (memory location is defined by the word immediately following the opcode).

Syntax: X(Rn).

Length: Two or three words.

Comment: Valid for source and destination.

Example 2: Move (copy) the contents at source address (F000h + R5) to destination (register R4).

Before operation: R4=A002h R5=050Ah Loc:0xF50A=0123h

Operation: MOV F000h(R5), R4

After operation: R4=0123h R5=050Ah Loc:0xF50A=0123h

Operands 2 nd operand mode Operator Cycles Length (words)
2 Register Any 3 2
2 Indexed, Symbolic or Absolute Any 6 3
1 N/A RRA, RRC, SWPB or SXT 4 2
1 N/A CALL or PUSH 5 2

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Teaching and classroom laboratories based on the “ez430” and "experimenter's board" msp430 microcontroller platforms and code composer essentials. OpenStax CNX. May 19, 2009 Download for free at http://cnx.org/content/col10706/1.3
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