CPI

 

 

Syntax: CPI 8-bit

Where  8-bit is an immediate data.

Byte: 2 byte

Addressing Mode: Immediate  Addressing

Working: 

1. This is Two byte instruction.

2. microprocessor will allocate First byte for opcode CPI and Second byte for immediate operand. 

3. This instruction compares the content of the register R with content of the Accumulator.

The comparison is done using subtraction of the content of register from the Accumulator. 

The content of Accumulator remains unchanged.

Conditions of Comarison:

 

1. If [A] < [R] then Cy flag is set i.e. Cy =1.

2. If [A] = [R]  then Z flag is set i.e Z=1.

3. If [A] > [R]  then Cy and Z flags are reset. i.e Cy = 0 and  Z = 0

4. Flag

Example: CPI 22H

where [A]= 11H

After execution of CPI 22H

[A] = 11H

 

2's complement subtraction:

A= 11 =  0001 0001

   = 22 =  0010 0010

1's complement of 22 = 1101 1101

2's complement of 22 =  1101 1110

 

                               1

                  A =   0001 0001

 2's copm.22=   1101 1110

                      0  1110  1111 

 

Cy = 1..............[complement the carry (according to 2's complement subtrsction)]

Z =  0

 

First condition of comparison is matched. i.e. [A]< 22H