1. The MSP430xxxx Department of Electrical and Computer Engineering
ECE 2560
The MSP430xxxx
Department of Electrical and
Computer Engineering
The Ohio State University
ECE Lecture 1

2. Today The MSP430 Microcontroller The Physical Chip/Processor
What is a microcontroller
The Physical Chip/Processor
Memory structure
Addressing Modes
ECE Lecture 1

3. The MSP430 Microcontroller
What is a microcontroller?
A microprocessor with memory and I/O port support directly on chip. It also includes controllers for interfaces such a JTAG, SPIO, A-to-D conversion on board.
With the support on chip, microcontrollers are very important in design and implementation of embedded systems.
ECE Lecture 1

4. The MSP430 A von-Neumann style architecture Key features
Ultralow-power architecture
0.1 uA RAM rentention
0.8 uA real-time clock mode
250 uA/MIPS active
High-performance A-to-D conversion
12-bit or 10-bit ADC, 12-bit dual-DAC
200 ksps
16-bit RISC processor features
Large Register file
Compact code design
27 core instructions
7 addressing modes
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5. The MSP430 Block Diagram of internal structure – high level
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6. MSP430 Memory structure – logical 16-bit addressable
64K bytes (64KB)
Amount of Flash/ROM and RAM vary by device
Last 16 words of Flash/ROM used for the Interrupt Vector Table
I/O is memory mapped
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7. Memory data organization
Bytes can be at even or odd addresses
Words are only at even addresses
The low byte of a word is at the even address.
The high byte of a word is at the odd address
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8. Memory dump Big endian and little endian (the 430)
Little endian is more logical but… (pg 27 of text)
If memory is dumped by the debugger
Addresses increase from low to high across a line
Display is low-order-byte high-order-byte
so $ is displayed $34 $12
bytes look reversed but consistent with
their address
Can be avoided by getting the dump in words versus bytes. (Will see this later in examples) (Code composer supports this)
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9. The MSP430 CPU
Incorporates features to support modern programming techniques (Don’t need go to’s)
The features
Calculated branching
Table processing
27 RISC instructions
7 addressing modes
All instructions use all the addressing modes
Full register access
Single cycle register operations (RISC)
Direct memory-to-memory transfers
Constant generator provides most used values
ECE Lecture 1

10. The MSP430 data path There are 16 registers Note bus structure
Contents are 16-bits
User has access to all registers
4 registers are special purpose
Note bus structure
MDB – Memory Data Bus
MAB – Memory Address Bus
Also have 2 internal bussed to deliver 2 operand to ALU
Diagram is called the datapath of the processor
See Users Guide
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11. General purpose registers
R4 thru R15
Registers are indistinguishable
Can be used as
Data Registers
Address Registers
Index values
Can be accessed with byte or word instructions
There is Register-Byte operation and Byte-Register operation – covered later
ECE Lecture 1

12. Addressing Modes MSP430 addressing modes
Addressing mode – the way in which the operand(s) of an instruction are accessed, i.e., the effective addresses are calculated.
7 modes supported
Register Mode – (Rn) – operands are in registers
Immediate Mode – #N – The operand is part of the instruction
Instructions have format OPCODE #OPERAND
Absolute Mode – &ADDR – The address of the operand is given by the word following the opcode
Instructions have format OPCODE &ADDRESS
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13. Addressing Modes (2) Remainder of addressing mode
Indexed Mode – X(Rn) – (Rn+X) points to (is the address of) the operand. The value X is the next word in the instruction stream after the OPCODE.
Symbolic Mode – ADDR – (PC+X) points to the operand. X is the next word.
Indirect Register Mode – Rn is used as a pointer to the operand.
Indirect Autoincrement - Rn is used as a pointer to the operand. After access Rn is incremented by 1 for .B instructions and by 2 for .W instructions
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14. Register Mode Addressing
Note gives action if only a byte
Form is
MOV.B R1,R2
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15. Immediate Mode addressing
Operand is part of instruction
Destination can be a register or a memory location.
If a register instruction is only 2 words
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16. Absolute Mode Addressing
One of operands can be a register
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17. Absolute Mode Addressing (2)
Effect
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18. Indexed Mode Addressing
Summary
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19. Indexed Mode Addressing (2)
Action
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20. Symbolic Mode Addressing
Summary
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21. Symbolic Mode Addressing (2)
Action
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22. Indirect Register Mode
Summary
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23. Indirect Register Mode (2)
Action
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24. Indirect Autoincrement Mode
Summary
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25. Indirect Autoincrement Mode (2)
Action
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26. Assignment
The MSP 430 Users Guide has been added to the course webpage.
The information of this lecture can be found there (section 3.3).
Quiz next week – (again)
Some 430 questions
ECE Lecture 1