Fetch - Execute Cycle
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Slide 1: Video
Digital TechnologyFurther Education (Key Stage 5)
This lesson contains 10 slides, with text slides and 1 video.
Lesson duration is: 15 minItems in this lesson
Slide 1 - Video
RAM Module
16 memory locations
each containing 8 bits.
Some of these are instructions and some are variables.
Some of these are instructions and some are variables.
Address
Data
0
0010 1110
1
0001 1111
2
1000 0100
3
0100 1101
4
0000 0000
5
0000 0000
6
0000 0000
7
0000 0000
8
0000 0000
9
0000 0000
10
0000 0000
11
0000 0000
12
0000 0000
13
0000 0000
14
0000 0011
15
0000 1110
Slide 2 - Slide
6 Registers
4 Memory Data Registers
1 Memory Address Register (MAR)
aka Instruction Address Register
1 Current Instruction Register (CIR)
1 Current Instruction Register (CIR)
aka Instruction Register
Memory Data Register A
Memory Data Register B
Memory Data Register C
Register D
Memory Address Register
Current Instruction Register
Slide 3 - Slide
RAM Module
16 memory locations
each containing 8 bits.
Some of these are instructions and some are variables.
Some of these are instructions and some are variables.
Address
Data
0
0010 1110
1
0001 1111
2
1000 0100
3
0100 1101
4
0000 0000
5
0000 0000
6
0000 0000
7
0000 0000
8
0000 0000
9
0000 0000
10
0000 0000
11
0000 0000
12
0000 0000
13
0000 0000
14
0000 0011
15
0000 1110
Memory Data Register A
Memory Data Register B
Memory Data Register B
Memory Data Register B
Memory Address Register
Current Instruction Register
Slide 4 - Slide
Instruction Table
Instruction
Description
4-bit Opcode
Address or Registers
LOAD_A
Read RAM location into Register A
0010
4-bit RAM address
LOAD_B
Read RAM location into Register B
0001
4-bit RAM address
STORE_A
Write from Register A into RAM location
0100
4-bit RAM address
ADD
Add two Registers, store result into second Register
1000
2-bit Register ID,
2-Bit Register ID
Slide 5 - Slide
RAM Module
16 memory locations
each containing 8 bits.
Some of these are instructions and some are variables.
Some of these are instructions and some are variables.
Address
Data
0
0010 1110
1
0001 1111
2
1000 0100
3
0100 1101
4
0000 0000
5
0000 0000
6
0000 0000
7
0000 0000
8
0000 0000
9
0000 0000
10
0000 0000
11
0000 0000
12
0000 0000
13
0000 0000
14
0000 0011
15
0000 1110
Memory Data Register A
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Address Register
0000 0000
Current Instruction Register
0000 0000
Slide 6 - Slide
RAM Module
16 memory locations
each containing 8 bits.
Some of these are instructions and some are variables.
Some of these are instructions and some are variables.
Address
Data
0
0010 1110
1
0001 1111
2
1000 0100
3
0100 1101
4
0000 0000
5
0000 0000
6
0000 0000
7
0000 0000
8
0000 0000
9
0000 0000
10
0000 0000
11
0000 0000
12
0000 0000
13
0000 0000
14
0000 0011
15
0000 1110
Memory Data Register A
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Address Register
0000 0000
Current Instruction Register
0000 0000
Slide 7 - Slide
RAM Module
16 memory locations
each containing 8 bits.
Some of these are instructions and some are variables.
Some of these are instructions and some are variables.
Address
Data
0
0010 1110
1
0001 1111
2
1000 0100
3
0100 1101
4
0000 0000
5
0000 0000
6
0000 0000
7
0000 0000
8
0000 0000
9
0000 0000
10
0000 0000
11
0000 0000
12
0000 0000
13
0000 0000
14
0000 0011
15
0000 1110
Memory Data Register A
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Address Register
0000 0000
Current Instruction Register
0010 1110
Slide 8 - Slide
RAM Module
16 memory locations
each containing 8 bits.
Some of these are instructions and some are variables.
Some of these are instructions and some are variables.
Address
Data
0
0010 1110
1
0001 1111
2
1000 0100
3
0100 1101
4
0000 0000
5
0000 0000
6
0000 0000
7
0000 0000
8
0000 0000
9
0000 0000
10
0000 0000
11
0000 0000
12
0000 0000
13
0000 0000
14
0000 0011
15
0000 1110
Memory Data Register A
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Data Register B
0000 0000
Memory Address Register
0000 0000
Current Instruction Register
0010 1110
OPCODE
Slide 9 - Slide
Instruction Table
Instruction
Description
4-bit Opcode
Address or Registers
LOAD_A
Read RAM location into Register A
0010
4-bit RAM address
LOAD_B
Read RAM location into Register B
0001
4-bit RAM address
STORE_A
Write from Register A into RAM location
0100
4-bit RAM address
ADD
Add two Registers, store result into second Register
1000
2-bit Register ID,
2-Bit Register ID
