duel电子信息工程微处理器外文翻译外文文献英文文献

2021年1月21日发(作者：词组)
外文资料

所译外文资料：

1.
作者

is, , r
2.
书名
:
Principles of Optical Disk Systems
3.
出版时间：
1991
年
9
月

4.
所译章节：
Session 2/Chapter9, Session 2/Chapter 11
原文：

Microprocessor
One of the key inventions in the history of electronics, and in fact one of the most important inventions
ever period, was the transistor. As time progressed after the invention of LSI integrated circuits, the tech no
logy improved and chips became smaller, faster and cheaper. The functions performed by a processor were
impleme nted using several differe nt logic chips. In tel was the first compa ny to in corporate all of these logic
components into a single chip, this was the first microprocessor. A microprocessor is a complete computatio n
engine that is fabricated on a sin gle chip. A microprocessor executes a collect ion of mach ine in struct ions
that tell the processor what to do. Based on the in struct ions, a microprocessor does three basic thin gs:
ing the ALU (Arithmetic/Logic Uni t), a microprocessor can perform mathematical operations like addition,
subtraction, multiplication and division; 2.A microprocessor can move data from one memory location to
another; 3.A microprocessor can make decisions and jump to a new set of in structi ons based on those decisi
ons.
There may be very sophisticated things that a microprocessor does, but those are its three basic
activities. Microprocessor has an address bus that sends an address to memory, a data bus that can send data
to memory or receive data from memory, an RD(read) and WR(write) line that lets a clock pulse seque nee the
processor and a reset line that resets the program coun ter to zero(or whatever) and restarts executio n. And let
'
assume that both the address and data buses are 8 bits wide here.
Here are the comp onents of this simple microprocessor:
1.
Registers A, B and C are simply latches made out of flip-flops.
2.
The address latch is just like registers A, B and C.
3.
The program coun ter is a latch with the extra ability to in creme nt by 1 whe n told to do so, and also
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to reset to zero whe n told to do so.
4. The ALU could be as simple as an 8-bit adder, or it might be able to add, subtract, multiply and divide
8-bit values. Let
'
assume the latter here.
5. The test register is a special latch that can hold values from comparisons performed in the ALU. An
ALU can normally compare two numbers send determine if they are equal, if one is greater than the
other, etc. The test register can also no rmally hold a carry bit from the last stage of the adder. It stores
these values in flip-flops and the n the in struct ion decoder can use the values to make decisi ons.
6. There are six boxes marked 3-State
”
These are tri-state buffers. A tri-state buffer can pass a 1, a 0 or
it can essentially disconnect its output. A tri-state buffer allows multiple outputs to connect to a wire, but
only one of the n to actually drive a 1or a 0 onto the line.
7. The instruction register and instruction decoder are responsible for controlling all of the other comp
onen ts.
Although they are not show n in this diagram, there would be con trol li nes from the in struct ion decoder
that would:
1.
Tell the A register to latch the value currently on the data bus
2.
Tell the B register to latch the value currently on the data bus
3.
Tell the C register to latch the value curre ntly on the data bus
4.
Tell the program counter register to latch the value currently on the data bus
5.
Tell the address register to latch the value curre ntly on the data bus
6.
Tell the in struct ion register to latch the value curre ntly on the data bus
7.
Tell the program coun ter to in creme nt
8.
Tell the program coun ter to reset to zero
9.
Activate any of the six tri-state buffers (six separate lin es)
10.
Tell the ALU what operati on to perform
11.
Tell the test register to latch the ALU
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test bits
12.
Activate the RD line
13.
Activate the WR line
Comi ng into the in structio n decoder are the bits from the best register and clock line, as well as the bits
from the in struct ion register.
RAM and ROM The address and data buses, as well as the RD and WR lines connect either to RAM or
ROM
—

gen erally both. In our sample microprocessor, we have an address bus 8 bits wide and a data bus 8
bits wide. That means that the microprocessor an address (2
n
) 256 bytes of the memory and it can read or
write 8 bits of the memory at a time. Let
'
assume that this simple microprocessor has 128 bytes of ROM
starting at address 0 and 128 bytes of RAM starting at address 128.
ROM stands for read-only memory. A ROM chip is programmed with a permanent collection of pre-set
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bytes. The address bus tells the ROM chip which byte to get and place on the data bus. When the RD line cha
nges state, the ROM chip prese nts the selected byte onto the data bus.
RAM sta nds for ran dom-access memory. RAM contains bytes of in formatio n, and the microprocessor
can read or write to those bytes depe nding on whether the RD or WR line is sig naled. One problem with
today's RAM chips is that they forget everythi ng once the power goes off. That is why the computer n eeds
ROM.
By the way, nearly all computers contain some amount of ROM (it is possible to create a simple computer
that contains no RAM
—

many microcontrollers do this by placing a handful of RAM bytes on the processor
chip itself
—

but gen erally impossible to create one that contains no ROM).
On a PC, the ROM is called the BIOS (Basic Input/Output System). When the microprocessor starts, it begi ns
executi ng in struct ions it fin ds in the BIOS. The BIOS in structi ons do things like test the hardware in the
mach ine, and the n it goes to the hard disk to fetch the boot sector. This boot sector is ano ther small program,
and the BIOS store it in RAM after reading it off the disk. The microprocessor then begins executi ng the boot
sector
'
in structi ons from RAM. The boot sector program will tell the microprocessor to fetch something else
from the hard disk into RAM, which the microprocessor then executes, and so on. This is how the
microprocessor loads and executes en tire operati ng system.
Microprocessor In struct ions Even the in credibly simple microprocessor show n here will have a fairly
large set of in struct ions that it can perform. The collect ion of in structi ons is impleme nted as bit patter ns,
each one of which has a differe nt mea ning whe n loaded in to the in structio n register. Huma ns are not
particularly good at rememberi ng bit patter ns, so a set of short words are defi ned to represe nt the differe nt
bit patter ns. This collect ion of words is called the assembly Ian guages of the processor. An assembler can
tran slate the words into their bit patter ns very easily, and the n the output of assembler is placed in memory
for the microprocessor to execute. If you use C Ian guage program ming, a C compiler will tran slate the C code
into assembly Ian guage.
So now the questio n is, How do all of these in struct ions look in ROM?
”
Each of these assembly Ian
guage in struct ions must be represe nted by a binary nu mber. These nu mbers all know as recodes. The in
structi on decoder n eeds to turn each of recodes into a set of sig nals that drive the differe nt comp onents in
side the microprocessor. Let 'stake the ADD in structio n as an example and look at what it n eeds to do.
During the first clock cycle, we need to actually load the instruction. Therefore the instruction decoder
needs to: activate the tri-state buffer for the program counter; activate the RD line; activate the data-i n tri-state
buffer; latch the in struct ion into the in structi on register.
During the second clock cycle, the ADD instruction is decoded. It needs to do very little: set the
operation of ALU to addition; latch the output of the ALU into the C register.
During the third clock cycle, the program coun ter is in creme nted (in theory this could be overlapped
into the sec ond clock cycle).
Every in struct ion can be broke n dow n as a set of seque need operati ons like these that man ipulate
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the comp onents of microprocessor in the proper order. Some in struct ion s, like this ADD in struct ion, might
take two or three clock cycles. Others might take five or six clock cycles.
Microprocessor Performanee The number of transistors available has a huge effect on the performa nee
of a processor. As see n earlier, a typical in struct ion in a processor like an 8088 took 15 clock cycles to
execute. Because of the desig n of the multiplier, it took approximately 80 cycles just to do one 16-bit
multiplication on the 8088. With more transistors, much more powerful multipliers capable of sin gle-cycle
speeds become possible.
More tran sistors also allow for a tech no logy called pipeli nin g. I n a pipeli ned architecture, i nstructio n
executi on overlaps. So even though it might take five clock cycles to execute each in struct ion, there can be
five in struct ions in various stages of executio n simulta neously. That way it looks like one in struct ion
completes every clock cycle.
Many moder n processors have multiple in structio n decoders, each with own pipeli ne. This allows for
multiple instruction streams, which means that more than one instruction can complete during each clock cycle.
This tech nique can be quite complex to impleme nt, so it can be lots of tran sistors.
The trend in processor desig n has bee n toward full 32-bit ALU with fast floati ng point processors built
in and pipeli ned executi on with multiple in struct ion streams. There has also bee n a tendency toward special
instructions that make certain operations particularly efficient. There has also been the addition of hardware
virtual memory support and L1 cach ing on the processor chip. All of these trends push up the transistor count,
leading to the multi-million transistor powerhouses available today. These processors can execute about one
billio n in struct ions per sec ond!
The Operational Amplifier will continue to be a vital component of analog design because it is a fun dame
ntal comp onent. Each gen erati on of electro nic equipme nt in tegrates more fun cti ons on silic on and takes
more of the an alog circuitry in side the IC. As digital applicati ons in crease, an alog applicati ons also in
crease because the predo minant supply of data and in terface applicati ons are in the real world, and the real
world is an an alog world.
The LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is intern
ally set to 20 to keep exter nal part count low, but the additi on of an exter nal resistor and capacitor betwee n
pins 1 and 8 will in crease the gain to any value from 20 to in puts are ground referenced while the
output automatically biases to on e-half the supply voltage. The quiesce nt power drain is only 24 mill watts
when operating from a 6 volt supply, making the LM386 ideal for battery operation.
A Crystal is a basic piezoelectric quartz crystal. On its own, it cannot gen erate electrical clocks. It has to
be connected to a clock oscillator to get a clock waveform. There are two kinds of crystals: Series Resonant,
which can be modeled as a high Q series LC circuit, and Parallel Resonant, which can be modeled as a high Q
parallel LC circuit. A Crystal Oscillator is an oscillator with the crystal as the feedback eleme nt. There are other
kinds of oscillators with active or passive feedback comp onen ts, but the crystal oscillator provides the most
accurate and stable output freque ncy. Crystal oscillators are the preferred clock
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