8087 MICROPROCESSOR and diagram with definition.pdf

2
Compatible Processor and Coprocessor
Processors
1. 8086 & 8088
2. 80286
3. 80386DX
4. 80386SX
5. 80486DX
6. 80486SX
Coprocessors
1. 8087
2. 80287,80287XL
3. 80287,80387DX
4. 80387SX
5. It is Inbuilt
6. 80487SX

INTRODUCTION
 8087 was the first math coprocessor for 16-bit
processors designed by Intel.
 It was built to pair with 8086 and 8088.
 The purpose of 8087 was to speed up the computations
involving floating point calculations.
 Addition, subtraction, multiplication and division of
simple numbers is not the coprocessor’s job.
 It does all the calculations involving floating point
numbers like scientific calculations and algebraic
functions.
3

INTRODUCTION
 By having a coprocessor, which performs all the calculations,
it can free up a lot of CPU’s time.
 This would allow the CPU to focus all of its resources on the
other functions it has to perform.
 This increases the overall speed and performance of the
entire system.
 This coprocessor introduced about 60 new instructions
available to the programmer.
 All the mnemonics begin with “F” to differentiate them from
the standard 8086 instructions.
 For e.g.: in contrast to ADD/MUL, 8087 provide FADD/FMUL.
4

INTRODUCTION
 Math coprocessor is also called as:
 Numeric Processor Extension (NPX)
 Numeric Data Processor (NDP)
 Floating Point Unit (FPU)
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ARCHITECTURE OF 8087
 8087 coprocessor is designed to operate with 8086
microprocessor.
 The microprocessor and coprocessor can execute
their respective instructions simultaneously.
 Microprocessor interprets and executes the normal
instruction set and the coprocessor interprets and
executes only the coprocessor instructions.
 All the coprocessor instructions are ESC
instructions, i.e. they start with “F”.
6

ARCHITECTURE OF 8087
 The internal structure of 8087 coprocessor is
divided into two major sections:
 Control Unit (CU)
 Numerical Execution Unit (NEU)
8

CONTROL UNIT (CU)
 It interfaces coprocessor to the microprocessor
system bus.
 It also synchronize the operation of the
coprocessor and the microprocessor.
 This unit has a Control Word, Status Word and
Data Buffer.
 If an instruction is ESC instruction, then
coprocessor executes it.
 If not, then microprocessor executes.
9

NUMERIC EXECUTION UNIT (NEU)
 This unit is responsible for executing all
coprocessor instructions.
 It has an 8 register stack that holds the operands
for instructions and result of instructions.
 The stack contains 8 registers that are 80-bits wide.
 Numeric data is transferred inside the coprocessor
in two parts:
 64-bit mantissa bus
 16-bit exponent bus
10

STATUS REGISTER
 Status Register tells the overall status of 8087
coprocessor.
 It is a 16-bit register.
 It is accessed by executing the FSTSW instruction.
 This instruction stores the contents of status
register into memory.
 Once the status is stored in memory, the bit
positions of the status register can be examined. 12

STATUS REGISTER
 Busy: It indicates that the coprocessor is busy
executing the task.
 Condition Codes (C0-C3): They indicate various
conditions about the coprocessor.
 Top of Stack: It indicates a register as top of stack
register, out of the eight stack registers.
 Exception Flag: It is set if any of the exception flag
bits (SF, PR, UF, OF, ZD, DN, IO) are set. 13

STATUS REGISTER
 Stack Fault: It is not available in 8087. It is active
only in 80387 and above.
 Precision: It indicates that the result has exceeded
the selected precision.
 Underflow: It tells if the result is too small to fit in a
register.
 Overflow: It tells if the result is too large to fit in a
register. 14

STATUS REGISTER
 Zero Divide: It indicates that you try to divide a
non-zero value by zero.
 Denormalized: It indicates that at least one of the
operand is de-normalized.
 Invalid Operation: It indicates an invalid operation.
For e.g.: pushing more than eight items onto the
stack, attempting to pop an item off an empty stack
or taking the square root of a negative number.
15

CONTROL REGISTER
 Control Register controls the operating modes of 8087.
 It is also a 16-bit register.
 It performs rounding control and precision control.
 It is also used to do masking and unmasking of the
exception bits that correspond to the rightmost six bits
of the status register.
 FLDCW instruction is used to load the value into control
register. 17

CONTROL REGISTER
 Rounding Control: It determines the type of rounding or
truncating to be done.
00=Round to nearest or even
01=Round down towards minus infinity
10=Round up towards plus infinity
11=Chop or truncate towards zero
 Precision Control: It sets the precision of the result.
00=Single precision (short)
01=Reserved
10=Double precision (long)
11=Extended precision (temporary)
 Exception Masks: It determines that whether an error effects
the exception bits in the status register.
 If it is one, then the corresponding error is ignored.
 If it is zero and the corresponding error occurs, then it generates an
interrupt, and the corresponding bit in status register is set.
18

TAG REGISTER
19
Tag Values:
00 = Valid
01 = Zero
10 = Invalid
11 = Empty
TAG 7 TAG 6 TAG 5 TAG 4 TAG 3 TAG 2 TAG 1 TAG 0

TAG REGISTER
 Tag Register is used to indicate the contents of
each register in the stack.
 There are total 8 tags (Tag 0 to Tag 7) in this
register and each tag uses 2 bits to represent a
value.
 Therefore, it is a 16-bit register.
20
Tag Values:
00 = Valid
01 = Zero
10 = Invalid
11 = Empty
TAG 7 TAG 6 TAG 5 TAG 4 TAG 3 TAG 2 TAG 1 TAG 0

PIN DIAGRAM OF 8087
21
8
0
8
7
GND
GND
CLK
NC
NC
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
AD8
AD9
AD10
AD11
AD12
AD13
AD14
VCC
AD15
A16/S3
A17/S4
A18/S5
A19/S6
BHE/S7
RQ/GT1
INT
RQ/GT0
NC
NC
S2
S1
S0
QS0
QS1
BUSY
READY
RESET

INTERFACING OF 8086 AND 8087
 Multiplexed address-data bus lines are connected
directly from 8086 to 8087.
 The status lines and the queue status lines are
connected directly from 8086 to 8087.
 The Request/Grant (RQ/GT0 and RQ/GT1) signals
of 8087 are connected to RQ/GT0 and RQ/GT1 of
8086.
 BUSY signal of 8087 is connected to TEST pin of
8086.
22

EXCEPTION HANDLING
 The 8087 detects six different types of exception
conditions that occur during instruction execution.
These will cause an interrupt if unmasked and
interrupts are enabled.
 1) INVALID OPERATION
 2) OVERFLOW
 3) ZERO DIVISOR
 4) UNDERFLOW
 5) DENORMALIZED OPERAND
 6) INEXACT RESULT
23

SYNCHRONIZATION BETWEEN 8086 AND 8087
24
Escape
Activate
Test Pin
Execute
8086
Instruction
Wait
Deactivate
Test Pin
Monitor
8086
Wake up Co-processor
Wakeup 8086
8086 8087

DATA TYPES
 Internally, all data operands are converted to the
80-bit temporary real format.
 We have 3 types.
 •Integer data type
 •Packed BCD data type
 •Real data type
25

INSTRUCTION SET
 The 8087 instruction mnemonics begins with the
letter F which stands for Floating
 point and distinguishes from 8086.
 The 8087 detects an error condition usually called
an exception when it executing an
 instruction it will set the bit in its Status register.
 Types
 I. DATA TRANSFER INSTRUCTIONS.
 II. ARITHMETIC INSTRUCTIONS.
 III. COMPARE INSTRUCTIONS.
20-Nov-10
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DATA TRANSFERS INSTRUCTIONS
 REAL TRANSFER
 FLD Load real
 FST Store real
 FSTP Store real and pop
 FXCH Exchange registers
 INTEGER TRANSFER
 FILD Load integer
 FIST Store integer
 FISTP Store integer and pop 27

 FLD Source- Decrements the stack pointer by
one and copies a real number from a
 stack element or memory location to the new ST.
 •FLD ST(3) ;Copies ST(3) to ST.
 •FLD LONG_REAL[BX] ;Number from memory
copied to ST.
 FLD Destination- Copies ST to a specified stack
position or to a specified memory location .
 •FST ST(2) ;Copies ST to ST(2),and increment
stack pointer.
 •FST SHORT_REAL[BX] ;Copy ST to a memory at
a SHORT_REAL[BX]
28

 􀂾 FXCH Destination – Exchange the contents
of ST with the contents of a specified
 stack element.
 •FXCH ST(5) ;Swap ST and ST(5)
20-Nov-10
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 FILD Source – Integer load. Convert integer
number from memory to temporary-real
sformat and push on 8087 stack.
 •FILD DWORD PTR[BX] ;Short integer from
memory at [BX].
 FIST Destination- Integer store. Convert number
from ST to integer and copy to memory.
 •FIST LONG_INT ;ST to memory locations named
LONG_INT.
20-Nov-10
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ARITHMETIC INSTRUCTIONS.
FOUR BASIC ARITHMETIC FUNCTIONS:
ADDITION, SUBTRACTION, MULTIPLICATION, AND
DIVISION
 Addition
 FADD Add real
 FADDP Add real and pop
 FIADD Add integer
 Subtraction
 FSUB Subtract real
 FSUBP Subtract real and pop
 FISUB Subtract integer
31

 Multiplication
 FMUL Multiply real
 FMULP Multiply real and pop
 FIMUL Multiply integer
 Advanced
 FABS Absolute value
 FCHS Change sign
 FPREM Partial remainder
 FPRNDINT Round to integer
 FSCALE Scale
 FSQRT Square root
 FXTRACT Extract exponent and mantissa.
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 FADD ST(3), ST ;Add ST to ST(3), result in ST(3)
 •FADD ST,ST(4) ;Add ST(4) to ST, result in ST.
 •FADD ;ST + ST(1), pop stack result at ST
 •FADDP ST(1) ;Add ST(1) to ST. Increment stack pointer so
ST(1) become ST.
 •FSUB ST(2), ST ;ST(2)=ST(2) – ST.
 •FSUB Rate ;ST=ST – real no from memory.
 •FSUB ;ST=( ST(1) – ST)
 FSUBP - Subtract ST from specified stack element and put
result in specified stack
 element .Then increment the pointer by one.
 •FSUBP ST(1) ;ST(1)-ST. ST(1) becomes new ST
33

COMPARE INSTRUCTIONS.
 FCOM Compare real
 FCOMP Compare real and pop
 FCOMPP Compare real and pop twice
 FICOM Compare integer
 FICOMP Compare integer and pop
 FTST Test ST against +0.0
 FXAM Examine ST
 Transcendental Instruction.
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8087 MICROPROCESSOR and diagram with definition.pdf

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8087 MICROPROCESSOR and diagram with definition.pdf