參數(shù)資料
型號(hào)： Intel387 sx
廠商： Intel Corp.
英文描述： SX Math Coprocessor(32位數(shù)學(xué)協(xié)處理器)
中文描述： 山西數(shù)學(xué)協(xié)處理器（32位數(shù)學(xué)協(xié)處理器）
文件頁(yè)數(shù)： 21/47頁(yè)
文件大?。?/td> 443K
代理商： INTEL387 SX
Intel387
TM
SX MATH COPROCESSOR
3.6 Initialization
After FNINIT or RESET, the control word contains
the value 037FH (all exceptions masked, precision
control 64 bits, rounding to nearest) the same values
as in an Intel287 after RESET. For compatibility with
the 8087 and Intel287, the bit that used to indicate
infinity control (bit 12) is set to zero; however, re-
gardless of its setting, infinity is treated in the affine
sense. After FNINIT or RESET, the status word is
initialized as follows:
#
All exceptions are set to zero.
#
Stack TOP is zero, so that after the first push the
stack top will be register seven (111B).
#
The condition code C
3
–C
0
is undefined.
#
The B-bit is zero.
The tag word contains FFFFH (all stack locations
are empty).
The Intel386 Microprocessor and Intel387 Math Co-
Processor initialization software must execute a
FNINIT instruction (i.e., FINIT without a preceding
WAIT) after RESET. The FNINIT is not strictly re-
quired for the Intel386 software, but Intel recom-
mends its use to help ensure upware compatibility
with other processors. After a hardware RESET, the
ERROR
Y
output is asserted to indicate that an In-
tel387 Math CoProcessor is present. To accomplish
this, the IE (Invalid Exception) and ES (Error Sum-
mary) bits of the status word are set, and the IM bit
(Invalid Exception Mask) in the control word is
cleared. After FNINIT, the status word and the con-
trol word have the same values as in an Intel287
Math CoProcessor after RESET.
3.7 Processing Modes
The Intel387 SX Math CoProcessor works the same
whether the CPU is executing in real-addressing
mode, protected mode, or virtual-8086 mode. All ref-
erences to memory for numerics data or status infor-
mation are performed by the CPU, and therefore
obey the memory-management and protection rules
of the CPU mode currently in effect. The Intel387 SX
Math CoProcessor merely operates on instruc-
tions and values passed to it by the CPU and there-
fore is not sensitive to the processing mode of the
CPU.
The real-address mode and virtual-8086 mode, the
Intel387 SX Math CoProcessor is completely upward
compatible with software for the 8086/8087 and
80286/80287 real-address mode systems.
In protected mode, the Intel387 SX Math CoProces-
sor is completely upward compatible with software
for the 80286/80287 protected mode system.
The only differences of operation that may appear
when 8086/8087 programs are ported to the pro-
tected mode (not using virtual-8086 mode) is in the
format of operands for the administrative instruc-
tions FLDENV, FSTENV, FRSTOR, and FSAVE.
3.8 Programming Support
Using the Intel387 SX Math CoProcessor requires
no special programming tools, because all new in-
structions and data types are directly supported by
the assembler and compilers for high-level lan-
guages. All Intel386 Microprocessor development
tools that support Intel387 Math CoProcessor pro-
grams can also be used to develop software for the
Intel386 SX Microprocessors and Intel387 SX Math
CoProcessors. All 8086/8088 development tools
that support the 8087 can also be used to develop
software for the CPU and Math CoProcessor in real-
address mode or virtual-8086 mode. All 80286 de-
velopment tools that support the Intel287 Math Co-
Processor can also be used to develop software for
the Intel386 CPU and Intel387 Math CoProcessor.
4.0
HARDWARE SYSTEM
INTERFACE
In the following description of hardware interface,
the
Y
symbol at the end of a signal name indicates
that the active or asserted state occurs when the
signal is at a low voltage. When no
Y
is present after
the signal name, the signal is asserted when at the
high voltage level.
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