Transcript Microprocessor support circuits

MICROPROCESSOR
FUNCTION
Technician Series
Created Mar 2015
©prgodin @ gmail.com
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Microprocessor Function
• The microprocessor is a logic machine designed to follow
a repeating cycle of reading an instruction and executing
that instruction.
• The microprocessor relies on a built-in Instruction Set
that internally steers the data and controls mechanisms
toward its pre-programmed objective.
• The external instructions and data are obtained from
sources such as memory (ROM or RAM), or Input
systems (I/O) such as a keyboard or other external
source.
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Codes and Language
• The processor manipulates data in several different ways:
• Moves the data or addresses between different locations
• Add or subtracts values, more advanced devices can multiply,
divide and square root
• Performs logic operations such as complementing, inverting,
comparing, shifting, AND, OR, etc
• Instructions are in a binary pattern that the processor can
interpret. This is called Machine Language.
• When writing programs people use mnemonics, a short
abbreviated name, to make it easier to understand. This
is called Assembly Language.
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Codes and Language
• Assembly and Machine language are the lowest, most
basic way of programming a device.
• It would be very time consuming and technically difficult to
write an advanced set of codes or routines, called a
program, using these basic languages.
• Higher level languages, called programming languages,
are used to write more complex routines. Examples of
high level languages include C, C++, Java, VHDL, etc… .
A compiler is used to convert a high level language to a
machine language that can be stored and used by the
device.
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Optcodes and Operands
• At the device level, the microprocessor processes instructions
(OPTCODES) and data (OPERANDS).
• Sample of the Intel 8085 instructions (of 246 total), written in
mnemonics:
OPCODE
OPERAND
Description
MOV
Rd, Rs
Copy source register (Rs) to destination register (Rd)
ADD
M
Add content of memory to value in accumulator
STA
(address)
Copy address in accumulator register to memory
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Microprocessor Control
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Control
• The microprocessor has numerous inputs and outputs for
specific applications:
• Data/Instruction bus which is bi-directional (in or out of the
processor)
• Address bus which is unidirectional (out of the processor)
• Control lines which can be inputs or outputs but are typically
dedicated to specific purposes
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Microprocessor System
Address Bus
Control
Other I/O
Input Register
Output Register
ROM
μP
RAM
Data Bus
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Selecting
• There are 2 primary ways a microprocessor enables a
specific device on the data bus:
• Peripheral Mapping where the I/O or memory is selected
directly through the use of control outputs.
• Memory Mapping where the I/O or memory is selected
through the use of an address range.
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Decoding an Address in MemoryMapped I/O
A13
Address
16-bit
A
B
C
3 to 8 Decoder
Upper 3 bits A15
Y0
Y1
Y2
Y3
Y4
Y5
Y6
Y7
Individual
Device
Enables
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Device Select & Status
• S0, S1: Output indicates what
step the micro is on in its
processing cycle
• IO/M, Rd, Wr: Output to enable
selected device
• ALE: Output states when
address is on the AD bus
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Basic Control
• X1, X2: Clock input
• CLK: Clock out to other devices
• Reset in, out: Reset applied to
micro, it resets other devices
• Hold in: Stops microprocessor
• Hold Out: Micro acknowledges it
is in a hold (stopped) state
• SOD, SID: Serial data in/out
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Device Interrupt
• RST & INTR: input to the micro,
to tell it to execute an instruction
at a specific address
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Support Circuitry
• The instructor will provide a handout to analyze
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Programmable Logic
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Electronic Trends
• When learning electronics we used discrete single-
function chips as part of the lab activities.
• Electronics today is very different. What is more
commonly used are programmable logic devices:
• CPLD (Complex Programmable Logic Devices) for basic digital
logic operations
• FPGA (Field Programmable Gate Arrays) for more advanced digital
logic functions
• ARM and microcontrollers such as Arduino, Stamp, and many
others for processing capabilities and may be fully functional
computers with integrated RAM, ROM, I/O
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Embedded Systems
• An embedded system is a computer that is designed and
used as a dedicated function.
• Advantages of embedded systems are numerous:
• Size, power consumption and price is reduced. May be highly
portable.
• Integrated functions further reduce the amount of support circuitry
needed. Examples include ADCs, integrated sensors.
• Very efficient at its specific task.
• Firmware may be updated.
• Programmable logic is more universal, smaller, easily modified,
designs are easily transported, etc.
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Examples of Embedded Systems
• You likely own many embedded systems:
• Computer (devices such as HDD, MB and other peripherals have
embedded systems)
• Printer
• Cell Phone (typically ARM-based)
• MP3 Player
• Remotes
• Calculators
• Digital Camera
• Newer vehicle
• Newer appliances such as dishwashers, clothes washers,
microwaves, televisions and even toasters may have embedded
systems.
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Embedded Systems
• Embedded Systems have several significant
disadvantages to a technician:
• The physical chip may be custom-made or otherwise unavailable
• The chips are not universal and must remain with the specific
vendor
• The chip may be impossible to physically access
• The software to program the device is device-specific and may be
very expensive
• The program written for the embedded chip is proprietary and will
not be generally available
• The device input/output values and configurations may be
unknown, so it may be difficult to determine if the device is
functioning properly.
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Embedded System
• The instructor will hand out diagrams to analyze
END