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Semiconductor Group
46
On-Chip Peripheral Components
Table 7-2
Read-Modify-Write Instructions
lt is not obvious that the last three instructions in this list are read-modify-write instructions, but they
are. The reason is that they read the port byte, all 8 bits, modify the addressed bit, then write the
complete byte back to the latch.
The reason why read-modify-write instructions are directed to the latch rather than the pin is to avoid
a possible misinterpretation of the voltage level at the pin. For example, a port bit might be used to
drive the base of a transistor. When a "1" is written to the bit, the transistor is turned on. lf the CPU
then reads the same port bit at the pin rather than the latch, it will read the base voltage of the
transistor (approx. 0.7 V, i.e. a logic low level !) and interpret it as "0". For example, when modifying
a port bit by a SETB or CLR instruction, another bit in this port with the above mentioned
configuration might be changed if the value read from the pin were written back to the latch.
However, reading the latch rather than the pin will return the correct value of "1".
Instruction
Function
ANL
Logic AND; e.g. ANL P1, A
ORL
Logic OR; e.g. ORL P2, A
XRL
Logic exclusive OR; e.g. XRL P3, A
JBC
Jump if bit is set and clear bit; e.g. JBC P1.1, LABEL
CPL
Complement bit; e.g. CPL P3.0
INC
Increment byte; e.g. INC P4
DEC
Decrement byte; e.g. DEC P5
DJNZ
Decrement and jump if not zero; e.g. DJNZ P3, LABEL
MOV Px.y, C
Move carry bit to bit y of port x
CLR Px.y
Clear bit y of port x
SETB Px.y
Set bit y of port x
*
Содержание SAB 80515 Series
Страница 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Страница 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Страница 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Страница 22: ...Semiconductor Group 22 Memory Organization Figure 4 3 Mapping of the Lower Portion of the Internal Data Memory ...
Страница 30: ...Semiconductor Group 30 External Bus Interface Figure 5 1 a and b External Program Memory Execution ...
Страница 38: ...Semiconductor Group 38 On Chip Peripheral Components Figure 7 3 Output Driver Circuits of Ports 1 through 5 ...
Страница 59: ...Semiconductor Group 59 On Chip Peripheral Components Figure 7 16 a Functional Diagram Serial Interface Mode 0 ...
Страница 60: ...Semiconductor Group 60 On Chip Peripheral Components Figure 7 16 b Timing Diagram Serial Interface Mode 0 ...
Страница 61: ...Semiconductor Group 61 On Chip Peripheral Components Figure 7 17 a Functional Diagram Serial Interface Mode 1 ...
Страница 62: ...Semiconductor Group 62 On Chip Peripheral Components Figure 7 17 b Timing Diagram Serial Interface Mode 1 ...
Страница 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Страница 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Страница 111: ...Semiconductor Group 111 On Chip Peripheral Components Figure 7 54 Timing Diagram System Clock Output ...
Страница 113: ...Semiconductor Group 113 Interrupt System Figure 8 1 a Interrupt Structure of the SAB 80 C 515 80 C 535 ...
Страница 114: ...Semiconductor Group 114 Interrupt System Figure 8 1 b Interrupt Structure of the SAB 80 C 515 80 C 535 cont d ...
Страница 204: ...Semiconductor Group 204 Instruction Set XCH A Ri Operation XCH A Ri Bytes 1 Cycles 1 Encoding 1 1 0 0 0 1 1 i ...
Страница 215: ...Device Specifications Semiconductor Group 215 ...
Страница 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Страница 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Страница 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Страница 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Страница 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Страница 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Страница 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...
Страница 268: ...Device Specifications Semiconductor Group 268 AC Testing Input Output Waveforms AC Testing Float Waveforms ...