General Purpose Processors : Softwares Computer Science Engineering (CSE) Notes | EduRev

 Page 1


Embedded Systems Design: A Unified 
Hardware/Software Introduction 
1 
Chapter 3   General-Purpose Processors: 
Software 
Page 2


Embedded Systems Design: A Unified 
Hardware/Software Introduction 
1 
Chapter 3   General-Purpose Processors: 
Software 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
2 
Introduction 
• General-Purpose Processor 
– Processor designed for a variety of computation tasks 
– Low unit cost, in part because manufacturer spreads NRE 
over large numbers of units 
• Motorola sold half a billion 68HC05 microcontrollers in 1996 alone 
– Carefully designed since higher NRE is acceptable 
• Can yield good performance, size and power 
– Low NRE cost, short time-to-market/prototype, high 
flexibility 
• User just writes software; no processor design 
– a.k.a. “microprocessor” – “micro” used when they were 
implemented on one or a few chips rather than entire rooms 
Page 3


Embedded Systems Design: A Unified 
Hardware/Software Introduction 
1 
Chapter 3   General-Purpose Processors: 
Software 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
2 
Introduction 
• General-Purpose Processor 
– Processor designed for a variety of computation tasks 
– Low unit cost, in part because manufacturer spreads NRE 
over large numbers of units 
• Motorola sold half a billion 68HC05 microcontrollers in 1996 alone 
– Carefully designed since higher NRE is acceptable 
• Can yield good performance, size and power 
– Low NRE cost, short time-to-market/prototype, high 
flexibility 
• User just writes software; no processor design 
– a.k.a. “microprocessor” – “micro” used when they were 
implemented on one or a few chips rather than entire rooms 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
3 
Basic Architecture 
• Control unit and 
datapath 
– Note similarity to 
single-purpose 
processor 
• Key differences 
– Datapath is general 
– Control unit doesn’t 
store the algorithm – 
the algorithm is 
“programmed” into the 
memory 
 
Processor 
Control unit Datapath 
ALU 
Registers 
IR PC 
Controller 
Memory 
I/O 
Control 
/Status 
Page 4


Embedded Systems Design: A Unified 
Hardware/Software Introduction 
1 
Chapter 3   General-Purpose Processors: 
Software 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
2 
Introduction 
• General-Purpose Processor 
– Processor designed for a variety of computation tasks 
– Low unit cost, in part because manufacturer spreads NRE 
over large numbers of units 
• Motorola sold half a billion 68HC05 microcontrollers in 1996 alone 
– Carefully designed since higher NRE is acceptable 
• Can yield good performance, size and power 
– Low NRE cost, short time-to-market/prototype, high 
flexibility 
• User just writes software; no processor design 
– a.k.a. “microprocessor” – “micro” used when they were 
implemented on one or a few chips rather than entire rooms 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
3 
Basic Architecture 
• Control unit and 
datapath 
– Note similarity to 
single-purpose 
processor 
• Key differences 
– Datapath is general 
– Control unit doesn’t 
store the algorithm – 
the algorithm is 
“programmed” into the 
memory 
 
Processor 
Control unit Datapath 
ALU 
Registers 
IR PC 
Controller 
Memory 
I/O 
Control 
/Status 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
4 
Datapath Operations 
• Load 
– Read memory location 
into register  
• ALU operation 
– Input certain registers 
through ALU, store 
back in register 
• Store 
– Write register to 
memory location 
Processor 
Control unit Datapath 
ALU 
Registers 
IR PC 
Controller 
Memory 
I/O 
Control 
/Status 
10 
... 
... 
10 
+1 
11 
11 
Page 5


Embedded Systems Design: A Unified 
Hardware/Software Introduction 
1 
Chapter 3   General-Purpose Processors: 
Software 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
2 
Introduction 
• General-Purpose Processor 
– Processor designed for a variety of computation tasks 
– Low unit cost, in part because manufacturer spreads NRE 
over large numbers of units 
• Motorola sold half a billion 68HC05 microcontrollers in 1996 alone 
– Carefully designed since higher NRE is acceptable 
• Can yield good performance, size and power 
– Low NRE cost, short time-to-market/prototype, high 
flexibility 
• User just writes software; no processor design 
– a.k.a. “microprocessor” – “micro” used when they were 
implemented on one or a few chips rather than entire rooms 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
3 
Basic Architecture 
• Control unit and 
datapath 
– Note similarity to 
single-purpose 
processor 
• Key differences 
– Datapath is general 
– Control unit doesn’t 
store the algorithm – 
the algorithm is 
“programmed” into the 
memory 
 
Processor 
Control unit Datapath 
ALU 
Registers 
IR PC 
Controller 
Memory 
I/O 
Control 
/Status 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
4 
Datapath Operations 
• Load 
– Read memory location 
into register  
• ALU operation 
– Input certain registers 
through ALU, store 
back in register 
• Store 
– Write register to 
memory location 
Processor 
Control unit Datapath 
ALU 
Registers 
IR PC 
Controller 
Memory 
I/O 
Control 
/Status 
10 
... 
... 
10 
+1 
11 
11 
Embedded Systems Design: A Unified 
Hardware/Software Introduction, (c) 2000 Vahid/Givargis  
5 
Control Unit 
• Control unit: configures the datapath 
operations 
– Sequence of desired operations 
(“instructions”) stored in memory – 
“program”  
• Instruction cycle – broken into 
several sub-operations, each one 
clock cycle, e.g.: 
– Fetch: Get next instruction into IR 
– Decode: Determine what the 
instruction means 
– Fetch operands: Move data from 
memory to datapath register 
– Execute: Move data through the 
ALU 
– Store results: Write data from 
register to memory 
Processor 
Control unit Datapath 
ALU 
Registers 
IR PC 
Controller 
              Memory 
I/O 
Control 
/Status 
10 
... 
... 
load R0, M[500] 
500 
501 
100 
inc R1, R0 101 
store M[501], R1 102 
R0 R1