DEC m |
Decrement operand m. |
Function: |
m
m - 1 |
Format: |
m: may be r, (HL), (IX + d), (IY + d) |
r |
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(HL) |
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35 |
(IX + d) |
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byte 1: DD |
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byte 2: 35 |
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byte 3: offset data |
(IY + d) |
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byte 1: FD |
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byte 2: 35 |
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byte 3: offset data |
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r may be any one of:
- A
- 111
- B
- 000
- C
- 001
- D
- 010
- E
- 011
- H
- 100
- L
- 101
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Description: |
The contents of the location addressed by the specified operand are decremented and stored back at that location. m is defined in the description of the similar INC instructions. |
Data Flow: |
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Timing: |
m: |
M cycles: |
T states: |
usec @ 2 MHz: |
r
(HL)
(IX + d)
(IY + d) |
1
3
6
6 |
4
11
23
23 |
2
5.5
11.5
11.5 |
|
Addressing Mode: |
r: implicit; (HL): indirect; (IX + d), (IY+d): indexed. |
Byte Codes: |
DEC r
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Flags: |
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Example: |
DEC C |
OBJECT CODE |
Before: |
After: |
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