Instruction 8085
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Detailed Review of the 8085 Instruction Set
1
8085 Instruction Set The 8085 instructions can be classified as follows:
Data transfer operations • • • •
2
Between registers Between memory location and a register Direct write to a register / memory Between I/O device and accumulator
Arithmetic operations (ADD, SUB, INR, DCR)
Logic operations
Branching operations (JMP, CALL, RET)
8085 Instruction Types
3
8085 Instruction Types
4
8085 Instruction Types
5
Simple Data Transfer Operations
Examples:
6
MOV MOV MVI
B,A C,D D,47
47 4A 16 47
From ACC to REG Between two REGs Direct-write into REG D
Simple Data Transfer Operations
Example:
OUT 05
D3 05
Contents of ACC sent to output port number 05. 7
Simple Memory Access Operations
8
Simple Memory Access Operations
9
Arithmetic Operations
10
Arithmetic Operations
11
Arithmetic Operations
12
Arithmetic Operations
13
Overview of Logic Operations
14
Logic Operations
15
Logic Operations
16
Logic Operations
17
Branching Operations
Note: This is an unconditional jump operation. It will always force the program counter to a fixed memory address continuous loop ! 18
Branching Operations
Conditional jump operations are very useful for decision making during the execution of the program.
19
Example Write a 8085 machine code program:
20
Read two different memory locations
Add the contents
Send the result to output port 02 (display) if there is no overflow
Display “FF” if there is an overflow
Stop
Example 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 21
LDA
2050
MOV LDA
B,A 2051
ADD JNC
B 2013
MVI
A,FF
STA 2053 HLT
3A 50 20 47 3A 51 20 80 D2 13 20 3E FF 32 53 20
Load contents of memory location 2050 into accumulator
Save the first number in B Load contents of memory location 2051 into accumulator
Add accumulator with B Jump to 2013 if no carry !
Direct write FF into accumulator Store accumulator contents at 2053 Stop
8255 Features: • 3 8-bit IO ports PA, PB, PC • PA can be set for Modes 0, 1, 2. PB for 0,1 and PC for mode 0 and for BSR. • PC has 2 4-bit parts: PC upper (PCU) and PC lower (PCL), each can be set independently for 1 or O. Each PC bit can be set/reset individually in BSR mode. • PA and PCU are Group A (GA) and PB and PCL are Group B (GB) 22
Pin configuration
23
A1
A0
Select
0
0
PA
0
1
PB
1
0
PC
1
1
Control reg.
24
25
26
1
8085 Instruction Set The 8085 instructions can be classified as follows:
Data transfer operations • • • •
2
Between registers Between memory location and a register Direct write to a register / memory Between I/O device and accumulator
Arithmetic operations (ADD, SUB, INR, DCR)
Logic operations
Branching operations (JMP, CALL, RET)
8085 Instruction Types
3
8085 Instruction Types
4
8085 Instruction Types
5
Simple Data Transfer Operations
Examples:
6
MOV MOV MVI
B,A C,D D,47
47 4A 16 47
From ACC to REG Between two REGs Direct-write into REG D
Simple Data Transfer Operations
Example:
OUT 05
D3 05
Contents of ACC sent to output port number 05. 7
Simple Memory Access Operations
8
Simple Memory Access Operations
9
Arithmetic Operations
10
Arithmetic Operations
11
Arithmetic Operations
12
Arithmetic Operations
13
Overview of Logic Operations
14
Logic Operations
15
Logic Operations
16
Logic Operations
17
Branching Operations
Note: This is an unconditional jump operation. It will always force the program counter to a fixed memory address continuous loop ! 18
Branching Operations
Conditional jump operations are very useful for decision making during the execution of the program.
19
Example Write a 8085 machine code program:
20
Read two different memory locations
Add the contents
Send the result to output port 02 (display) if there is no overflow
Display “FF” if there is an overflow
Stop
Example 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 21
LDA
2050
MOV LDA
B,A 2051
ADD JNC
B 2013
MVI
A,FF
STA 2053 HLT
3A 50 20 47 3A 51 20 80 D2 13 20 3E FF 32 53 20
Load contents of memory location 2050 into accumulator
Save the first number in B Load contents of memory location 2051 into accumulator
Add accumulator with B Jump to 2013 if no carry !
Direct write FF into accumulator Store accumulator contents at 2053 Stop
8255 Features: • 3 8-bit IO ports PA, PB, PC • PA can be set for Modes 0, 1, 2. PB for 0,1 and PC for mode 0 and for BSR. • PC has 2 4-bit parts: PC upper (PCU) and PC lower (PCL), each can be set independently for 1 or O. Each PC bit can be set/reset individually in BSR mode. • PA and PCU are Group A (GA) and PB and PCL are Group B (GB) 22
Pin configuration
23
A1
A0
Select
0
0
PA
0
1
PB
1
0
PC
1
1
Control reg.
24
25
26
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