EEE226

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EEE226

• DR. ZAINI ABDUL HALIM

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Flag

• The flag are set or reset after the execution of
  an arithmetic or logic operation data copy
  instructions do not affect any flags.
• Z-Zero set to 1 when the result is zero,
  otherwise it is reset
• CY-Carry operation has a carry, CY is 1,
  otherwise it is 0.
• S-Sign is set if bit D7 of the result is 1,
  otherwise it is reset.
• P-Parity set if the result has an even number of
  1s, odd number of 1s, the flag is reset.
• AC-Auxiliary Carry, carry is generated by digit
  D3 and passed to D4, the AC flag is set.

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Logical Operation

• AND, Or, exclusive OR-Any 8 bit number, or the
  contents of a register or of a memory location
  The result are stored in accumulator. The result
  are stored in acc.
• ANA D Assume A 54H D 82H
• 54H 01010100
• 82H 10000010
• 00000000
• Flag S0, Z1, P1, AC0
• , CY0
• ANI 97H Assume AA3H
• A3H 10100011
• 97H 10010111
• 10000011 S1, Z0, AC1, P0, CY0

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Logical Operation

• Rotate-each bit in acc can be shifted either left
  or right to the next position.
• RAR rotate acc right through carry
• RRC - rotate acc right bit D0 is placed in the
  position of D7 As well as in the carry flag

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Logical operation

• Compare-any 8 bit number, or the contents of the
  register or a memory location can be compared for
  equality, greater than or less than with the
  contents of acc. (acc operands)
• Altreg/Mem C1 and Z0
• AReg/Mem Z1, C0
• AgtReg/Mem C and Z0
• Example CMP B compare with acc
• Assume A 57H, B62H
• A57H01010111
• B62H01100010
• After execution A 57H and B62H
• S1, Z0, AC1, P1, CY1

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Cont..

• CPI compare Immediate with Acc
• Example CPI 0C2H

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Logical operation

• Complement The contents of the acc can be
  complemented, 0 to 1 and 1 to 0.
• Example
• CMA complement acc
• Assume the data byte of acc is 89H
• 89H 10001001
• After 0111011076H
• Example
• CMC complement carry

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Branching Operation

• This group of instruction alters the sequence of
  program execution either conditionally or
  unconditionally.
• Jump JC, JNC, JP (S0 JM(S1), JZ (Z1), JNZ
  (Z0)
• Example JZ start
• Call, return and Restart
• CALL DELAY
• RET

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Machine control operation

• Example Halt, Interrupt, NOP

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Data Format

• µp operates in binary. However real world
  operates in decimal number
• Therefore we need to code binary number into
  different media.
• In 8 bit processor, commonly used codes and data
  formats are ASCII, BCD, signed integer and
  unsigned integers

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Data Format

• ASCII Code- 7 bit alphanumeric code that
  represents decimal number, English alphabets. 8
  bit code, 1 bit to represent graphical character.
• BCD Code- used for decimal number, 0 to 9. 4
  bits are required to represent 10 digits. 8 bit
  register can accommodate two BCD numbers.
• Signed Integer- either positive or negative
  number. D7 is used for the sign, 0 represent the
  positive sign and 1 represents the negative
  sign.D0-D6 represent maginitude. The largest
  magnitude is 7F. All negative numbers are
  represented in 2s complement.

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Cont..

• Unsigned Integers 8 bits to represent magnitude.
  The largest number can be processed at one time
  is FFH. Numbers larger than 8 bits (such as
  16-bit or 24 bit) are processed by dividing them
  in groups of 8 bits.

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THANK YOU