PM0044

Pipelined execution

For the CALL instruction, it starts after the last cycle of the CALL execution.

Table 10.

Example of pipeline with Call/Jump

Add.

Instruction

Decode

Execute

lgth

Cycle

cycles

cycles

1

2

3

4

5

6

7

8

9

10

11

0xC000

INC A

1

1

1

F1

D

E

0xC001

JP label

1

1

3

D

E

0xC004

LDW X,[$5432.w]

X

X

4

F2

Flush

0xD010

label: NEG A

1

1

1

F1

D

E

0xD011

CALL label2

1

2

3

D

E

E

0xD014

LDW X,[$5432.w]

X

X

4

F2

Flush

0xD018

LDW X,[$7895.w]

X

X

4

F3

FS

0xE030

label2: INCW X

1

1

1

F1

D

E

Table 11. Legend

Symbol/Color

Definition

F

Fetch

FS

Fetch stalled

D

Decode

E

Execute

Doc ID 13590 Rev 3

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Pipelined execution

PM0044

register during the first execution cycle. As a result, in this cycle, the next instruction

(LD A,(X)) cannot be decoded since it reads the X register.

Table 12.

Example of stalled pipeline

Address

Instruction

Decode

Execute

lgth

Time (cycles)

cycles

cycles

1

2

3

4

7

8

9

10

11

12

13

14

0xC000

SUB SP, #20

1

1

2

F1

D

E

0xC002

LD A, #20

1

1

2

D

E

0xC004

BTJT 0x10, #5, to

1

2

5

F2

D

E

E

0xC009

INC A

1

1

1

F3

D

D

E

0xC00A

BTJF 0x20, #3, to

1

2

5

F1

D

E

E

0xC00F

NOP

X

X

1

Flush

0xC010

LDW X,[$5432.w]

X

X

4

F2

0xC014

LDW X,[$1234.w]

X

X

4

F3

0xD020

to: INCW Y

1

1

2

F1

D

E

0xD023

LD A,(X)

1

1

2

D

D

E

Table 13. Legend

Symbol/Color

Definition

F

Fetch

D

Decode stalled

D

Decode

E

Execute

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Doc ID 13590 Rev 3