The document describes the basic components of a microprocessor system including the CPU, registers, memory, buses, ALU, and control unit. It also explains the purpose and functioning of various registers in the CPU like the program counter, status register, index register, and stack pointer. The document concludes by discussing memory types, instruction sets, addressing modes, and providing some example assembly language programs to demonstrate data transfers and arithmetic operations.

1. Microprocessor Based Systems Design
(EEE 432)
F Mashuque Alamgir (FMA)
email: mashukalamgir@gmail.com

2. Computer Hardware Organization
CPU
Registers RAM | ROM
program data
storage storage
Control, data, address bus
ALU
Control
unit
output input
unit unit

3. Registers
• Register is a storage location in the CPU
• Used to hold data/address during execution of
an instruction
• Registers have faster access time than memory
• Number of registers available for programming
varies from µP to µP

4. Arithmetic Logic Unit (ALU)
• ALU does all arithmetic and logical operations
• ALU receives data from registers/memory and
performs the task
• ALU writes the result back to register/memory

5. Control unit
• Contains hardware instruction logic
• Decodes and monitors execution of
instructions
CPU
Registers RAM | ROM
program data
storage storage
Control, data, address bus
ALU
Control
unit input
output
unit unit

6. Bus
• Wires through which data and information
are interchanged between units
• Three types of bus (more later):
- Address bus - Data bus - Control bus
CPU
Registers RAM | ROM
program data
storage storage
Control, data, address bus
ALU
Control
unit input
output
unit unit

7. Program counter(PC)
• Register within CPU
• Holds the address of the next instruction to
be fetched from memory
• Goes through step by step counting
sequence - causes the computer to read
successive instruction stored in memory
• PC is modified with new address when there
is a jump or transfer or subroutine call
instruction
• example

8. Program counter (PC)
CPU Program memory
Data memory
A Stack
B
Status register
IX
SP
PC
Control, data, address bus
ALU
Control unit

9. Status register
• After an ALU operation following can occur
-carry/borrow for addition/subtraction
-overflow
-result zero, negative or positive
• Register which contains flags to indicate these
status of any processor operation
• Programmer can use these status condition for
program control
• example

10. Flags
• Carry flag
00110101
01000011
001111000
Carry 0
10000010
10100011
100100101
Carry 1

11. Index register
• Almost all µPs have an index register
• Holds a base address to be added to an
offset
• Base address and the offset forms the
effective address
• example

12. Index register
Effective
address Program
CPU memory
Data
Offset memory
A
address
B
Status register +
Base Stack
IX address
SP
PC
Control, data, address bus
ALU
Control unit

13. Stack pointer (SP)
• An area of RAM used for temporary storage of
data/return address is called stack
• SP is a register within CPU that points to the
next free location on the stack
• Each time a byte is put onto stack, SP is
decremented
• Each time a byte is retrieved from stack, SP is
incremented
• example

14. Stack pointer
CPU Program memory
Data memory
A Stack
B
Status register
IX
SP
PC
Control, data, address bus
ALU
Control unit

15. Stack pointer
A
B
Status register
IX 0044 0044
stack pointer
SP 0045 0045
PC 0046 0046
stack pointer
0047 0047
0048 0048 0048
0049 0049 value #2
ALU 004A 004A value #1
Control unit RAM before PUSH RAM after PUSH

16. Stack pointer
0044 0044
0045 stack pointer 0045
0046 0046 0046 stack pointer
0047 value #4 0047 0047
0048 value #3 0048 value #3
0049 value #2 0049 value #2
004A value #1 004A value #1
RAM before POP RAM after POP

17. Instruction set
• To program a µP, a variety of data manipulation,
arithmetic and logical instructions are featured for a
processor
• Instructions can be organised into functional groups
-Data movement -Arithmetic
-Logical -Bit manipulation
-Shift/rotate -Branch/Jump
-Subroutine call -Interrupt handling
-Miscellaneous
• More detail later (for a specific processor)

18. Addressing modes
• To perform an operation, operands are to be
supplied
• Operands can come from registers, memory
locations or directly as part of an instruction
• Addressing mode says from where the
operands come from
• Very common addressing modes are
-Immediate, direct, inherent, relative,
indexed (more detail later)

19. Memory
Random Access Memory (RAM)
• SRAM: static RAM – uses bipolar transistors
(4-6) and very fast but expensive
• DRAM: dynamic RAM – uses one transistor
and one capacitor – information stored in
capacitor – periodic refresh operation required

20. Memory
Read Only Memory (ROM)
• Mask-programmed read-only memory (MROM):
programmed when being manufactured
• Programmable read-only memory (PROM): the
memory chip can be programmed by the end user
– EPROM: programmable memory that can be
erased
– EEPROM: programmable memory that can be
erased by electrical signals and reprogrammed

21. Program
• A program is sequence of instructions
• A program can be written in
– Low level language e.g. assembly language
– High level language e.g. C, PASCAL
• Assembly language program is converted to
machine code by an assembler
• High level language is translated into
machine code by a compiler

22. Application of Microprocessor

23. HC11 Data transfer instruction
• Data transfer from memory to register
LDAA <opr> A ← [M]
LDAB <opr> B ← [M]
LDD <opr> D ← [M: M+1]
LDX <opr> IXH ← [M] , IXL ← [M+1]
LDY <opr>
LDS <opr> SPH ← [M] , SPL ← [M+1]
<opr> can be immediate, direct, extended, or index mode
Examples
LDAA $10
LDX #$1000

24. Data transfers from register to
memory
• STAA <M> ;Transfer contents of A to M; M ← [A]
• STAB <M> ;Transfer contents of B to M; M ← [B]
• STD <M> ;Transfer contents of D to M; M:M+1 ← [D]

25. Data transfers from register to
register
• TBA ; Transfer contents of B to A; A ← [B]
• TAB ; Transfer contents of A to B; B ← [A]
• TAP ; Transfer contents of A to CCR; CCR ← [A]
• TPA ; Transfer contents of CCR to A; A ← [CCR]

26. Example Program
Exercise 1: Load data into register and store it onto memory location
.area text
_main::
LDAA #$06 ; Loads accumulator A with hex value 6;
; This is written as A← 06
STAA $2025 ;Stores the content of accumulator A on to memory
;location $2025, $2025 ← [A]
LDAB $2025 ; Loads accumulator B with the contents of memory
;location $2025, B←[$2025]
STAB $1064 ; Stores the content of accumulator B on to memory
; location $1064, $1064 ← [B]
SWI ; Returns to monitor

27. Example Program
Exercise 2: Data exchange between registers
.area text
_main::
LDAB #$03 ; B ← $03
TBA ; Transfer contents of B to A; A ← [B]
STAA $1064 ; Store contents of A onto location $1064, $1064 ← [A]
SWI

28. Example Program
Exercise 3: Addition of two numbers
.area text
_main::
LDAB #$02 ; B ←$02
STAB $2025 ; $2025 ← [B]
LDAA #$01 ; A← $01
ADDA $2025 ; A←[A] + [$2025]
STAA $1064 ; $1064 ← [A]
SWI