Difference between revisions of "ADC"

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'''ADC A, n'''
 
'''ADC A, n'''
  
Machine Cycle Count: 2
+
Machine Cycle Count: 2<br>
 
OP Code #CE
 
OP Code #CE
  
Line 48: Line 48:
 
'''ADC A, (HL)'''
 
'''ADC A, (HL)'''
  
Machine Cycle Count: 2
+
Machine Cycle Count: 2<br>
 
OP Code #8E
 
OP Code #8E
  
 
''(HL)'' is the value of the byte of memory stored at the location where the address is the 16-bit value of registers H and L, where the register H is the upper byte, and register L is the lower byte.
 
''(HL)'' is the value of the byte of memory stored at the location where the address is the 16-bit value of registers H and L, where the register H is the upper byte, and register L is the lower byte.

Revision as of 22:17, 24 October 2010

Add With Carry


This opcode group adds the contents of register r (placeholder for specific implementations) and the carry flag to the contents of register A, to be stored in register A. The formula can be seen as A=A+r+CY. Since register A is an 8-bit register, you must make sure it wraps around appropriately to only contain an 8-bit value in the range of 0-0xFF (0-255).

The ADC operation code groups are known as follows:
1) ADC A, r
2) ADC A, n
3) ADC A, (HL)



Register F Flag Computation

The subtract flag bit is always reset to 0 for any ADC operation. The zero flag bit is set to 1 if the operation sets register A to 0, otherwise the zero flag is reset to 0. The carry flag bit is set to 1 if the operation causes a mathematical carry from bit 7. The half-carry flag bit is set to 1 if the operation causes a mathematical carry from bit 3.



ADC A, r

Machine Cycle Count: 1

OP Code Instruction Code Numbers:
#Register (in place of r)
8FA
88B
89C
8AD
8BE
8CH
8DL



ADC A, n

Machine Cycle Count: 2
OP Code #CE

n is the value of the byte of memory stored at the current immediate value, where the program counter is the 16-bit memory address being accessed.



ADC A, (HL)

Machine Cycle Count: 2
OP Code #8E

(HL) is the value of the byte of memory stored at the location where the address is the 16-bit value of registers H and L, where the register H is the upper byte, and register L is the lower byte.