1. Chapter 18 The 8051 Microcontroller
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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2. Introduction Common microprocessor components
Microprocessors designed for control applications are microcontrollers
CPU, RAM, ROM, timer/counter, and I/O ports
typical applications:
PC keyboard
automotive sensing and engine control
microwave oven
VCR
ATM
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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3. The 8051 Family of Microcontrollers
Basic architecture
4K X 8 ROM
128 X 8 RAM
two 16 bit counter/timers
interrupt control for 5 interrupt sources
serial I/O provided by TXD and RXD
four 8 bit parallel I/O ports
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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4. The 8051 Family of Microcontrollers
8052 features:
8K ROM
256 RAM
three counter/timers
8571 features:
internal EPROM in place of ROM
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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5. The 8051 Family of Microcontrollers
8031 features:
no internal ROM (accesses external ROM or EPROM for program instructions)
See figure 18-1 for a block diagram of the 8052 microcontroller
See table 18-1 for a summary of 8051 family features
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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6. Figure 18-1
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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7. 8051 Architecture
The same internal address space and external pins must be used for multiple functions
Similar to 8085A for multiplexed lines
See figure 18-2 for pin configuration
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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8. Figure 18-2
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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9. 8051 Architecture Port 0 is dual purpose: 8 bit bidirectional I/O
can sink up to 8 LS TTL loads in the LOW state
is a float for the HIGH state
low order multiplexed address/data bus
used to access external memory
demultiplexed using the ALE signal
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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10. 8051 Architecture Port 1 Port 2 is dual purpose:
8 bit bidirectional I/O
can sink or source up to 4 LS TTL loads
Port 2 is dual purpose:
high order address bus
used to access external memory
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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11. 8051 Architecture Port 3 is dual purpose: 8 bit bidirectional I/O
can sink or source up to 4 LS TTL loads
special purpose I/O to provide functions listed in table 18-2
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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12. William Kleitz Digital Electronics with VHDL, Quartus® II Version
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13. 8051 Architecture RST - a high resets the microcontroller
ALE/PROG – address latch enable and program pulse input for EPROM
PSEN – program store enable. Read strobe for external program memory
EA/VPP –
external access enables fetch of program code from external memory
21 V programming supply voltage for EPROM
XTAL1, XTAL2 – connections for crystal or external oscillator
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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14. 8051 Architecture Four areas within address spaces:
internal data memory
external data memory
internal code memory
external code memory
Using external memory ties up ports 0 and 2 for address and data bus
See figure 18-3
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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15. Figure 18-3
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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16. 8051 Architecture Use of address space in the 128 byte RAM
first 32 locations – data registers
next 6 locations – bit addressable memory locations
last 80 locations – general purpose data storage and stack
Special function registers are in address 80H to FFH
see table 18-3
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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17. William Kleitz Digital Electronics with VHDL, Quartus® II Version
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18. Interfacing to External Memory
64k or ROM and 64K of RAM can be added
Alternate functions of ports 2 and 0 support external addressing
Interfacing to a general purpose EPROM
see figure 18-5
Interfacing extra data memory
see figure 18-6
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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19. Figure 18-5
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20. Figure 18-6
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21. The 8051 Instruction Set
The complete instruction set summary is in Appendix H
Assembling 8051 instructions manually is difficult and will not exploit useful features
Using a commercial assembler package is the best option
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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22. The 8051 Instruction Set Addressing modes
examples of moving data into the accumulator:
MOV A,Rn:
MOV
MOV A,20H:
MOV A,P3:
MOV A,#64H:
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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23. The 8051 Instruction Set Program branching instructions
JMP label (unconditional jump)
JZ label (jump if accumulator zero)
JNZ label (jump if accumulator not zero)
JB bit,label (jump if bit set)
JNB bit,label (jump if bit not set)
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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24. The 8051 Instruction Set Program branching instructions (continued)
DJNZ Rn,label (decrement regsiter and jump if not zero)
CJNE Rn#data,label (compare immediate data to register and jump if not equal)
CALL label (call subroutine)
RET (return)
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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25. The 8051 Instruction Set Logical and bit operations
ANL A,Rn (AND register to accumulator)
ANL A,#data (AND data byte to accumulator)
ORL A,Rn (OR register to accumulator)
ORL A,#data (OR data byte to accumulator)
XRL A,Rn (Ex-OR register to accumulator)
XRL A,#data (Ex-OR data byte to accumulator)
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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26. The 8051 Instruction Set Logical and bit operations (continued)
RL A (rotate accumulator left)
RLC A (rotate accumulator left through carry)
RR A (rotate accumulator right)
RRC A (rotate accumulator right through carry)
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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27. The 8051 Instruction Set Arithmetic operations
ADD A,Rn (add register to accumulator)
ADD A,#data (add immediate data to accumulator)
SUBB A,Rn (subtract register from accumulator with borrow)
SUBB A,#data (subtract immediate data from accumulator with borrow)
INC A (increment accumulator)
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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28. The 8051 Instruction Set Arithmetic operations (continued)
INC Rn (increment register)
DEC A (decrement accumulator)
DEC Rn (decrement register)
MUL AB (multiply A times B)
DIV AB (divide A by B)
DA A (decimal adjust accumulator)
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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29. 8051 Applications
Bit handling instructions and built in I/O makes the 8051 useful for data acquisition and control applications
instruction timing
time delay
See examples 18-11, 18-12, and 18-13
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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30. Data Acquisition and Control System Application
The 8051 microcontroller module
8051 microcontroller
I/O buffers
address latch
EPROM interface
The ADC interface module
ADC0804 IC
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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31. Data Acquisition and Control System Application
The DAC interface module
MC1408
Applications
centigrade thermometer
temperature dependent PWM speed control
integrating solar radiometer
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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32. Summary
The 8051 microcontroller is different from a microprocessor because it has the CPU, ROM, RAM, timer/counter, and parallel and serial ports fabricated into a single IC.
Thirty two of the forty pins of the 8051 are used for the four 8 bit parallel I/O ports. Three of the ports share their function with the address, data, and control buses.
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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33. Summary
The address spaces of the 8051 are divided into four distinct areas: internal data memory, external data memory, internal code memory, and external code memory. The internal data memory is further divided into user RAM and special function registers (SFRs).
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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34. Summary
To interface to an external EPROM like the 2732, an octal D latch is required to demultiplex the address/data bus, which is shared with port 0. The external access (EA) pin is tied LOW and the (PSEN) output is used to enable the output of the EPROM.
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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35. Summary
Extra data memory and I/O ports can be interfaced by using the 8155 IC. The 8155 demultiplexes the address/data bus internally so an octal D latch is not required.
The MOV instruction is very powerful, providing the ability to move data almost anywhere internal or external to the microcontroller and to the I/O ports.
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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36. Summary
Program branching is accomplished by use of many different conditional and unconditional jumps and calls.
The 8051 instruction set provides the ability to work with individual bits, which makes it very efficient for on/off control operation. Instructions are available for all the logic functions, rotates, and bit manipulations.
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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37. Summary
Instructions are provided for all the basic arithmetic instructions: addition, subtraction, multiplication, division, incrementing, and decrementing.
Each instruction machine cycle takes 12 clock periods to complete. This means that if a 2 MHz crystal is used, each machine cycle takes microsecond to complete. One complete instruction takes 1, 2, or 4 machine cycles.
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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38. Summary
A 4 by 4 matrix keyboard can be scanned using bit operations on a single I/O port.
Interfacing an 8 bit analog to digital converter to an 8051 is accomplished with one port and two bits on a second port. The start-conversion LOW pulse is issued with bit setting instructions and the end-of-conversion signal is monitored with bit checking instructions.
William Kleitz Digital Electronics with VHDL, Quartus® II Version
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