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Semiconductor Group
155
Instruction Set
DEC
byte
Function:
Decrement
Description:
The variable indicated is decremented by 1. An original value of 00H will underflow
to 0FFH. No flags are affected. Four operand addressing modes are allowed:
accumulator, register, direct, or register-indirect.
Note:
When this instruction is used to modify an output port, the value used as the original
port data will be read from the output data latch,
not
the input pins.
Example:
Register 0 contains 7FH (01111111B). Internal RAM locations 7EH and 7FH
contain 00H and 40H, respectively. The instruction sequence
DEC
@R0
DEC
R0
DEC
@R0
will leave register 0 set to 7EH and internal RAM locations 7EH and 7FH set to
0FFH and 3FH.
DEC
A
Operation:
DEC
(A)
←
(A) – 1
Bytes:
1
Cycles:
1
DEC
Rn
Operation:
DEC
(Rn)
←
(Rn) – 1
Bytes:
1
Cycles:
1
Encoding:
0 0 0 1
0 1 0 0
Encoding:
0 0 0 1
1 r r r
*
Summary of Contents for SAB 80515 Series
Page 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Page 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Page 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Page 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Page 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Page 215: ...Device Specifications Semiconductor Group 215 ...
Page 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Page 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Page 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Page 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Page 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Page 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Page 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...