DCR
Syntax: DCR R
Where R can be any of the general purpose registers (A,B,C,D,E,H andL)
Byte: 1byte
Addressing Mode: Register Addressing
Working:
1.
2.
3.
4. Flag
Example: DCR B
Where [B]= 10H
After execution of DCR B
[B]= 0F H
SUB
Syntax: SUB R Where R can be any of the general purpose registers (A,B,C,D,E,H andL) Byte: 1byte Addressing Mode: Register Addressing Working: 1. 2. 3. 4. Flag Example: SUB B where [B] = 11H and [A]= 22H After execution of SUB B [A] = 11H [B] = 22H Program: write an ALP for 8bit subtraction of values present in Registers A and B where A carries 44H and B carries 30H. Store result at memory location 5000H. Label Mnemonics Comments Start: SUB B STA 5000H Stop: HLT Output: [5000H]= 14H LXI H, 4000H ; 4000= 90h MOV A,M ; a = 90h INX H ; 4001h where 4001= 40h MOV B, M ; b= 4 0h SUB B ; a = a - b ... A = 90 - 40= 50h INX H ; 4002h MOV M,A ; 4002h = 50h HLT
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