80C187 Datasheet, PDF (17/30 Pages) Intel Corporation – 80-BIT MATH COPROCESSOR

80C187
NPS1
x
1
0
0
0
0
0
0
0
0
NPS2
0
x
1
1
1
1
1
1
1
1
CMD0
x
x
0
0
1
1
0
0
1
1
Table 10 Bus Cycles Definition
CMD1
NPRD
NPWR
x
x
x
x
x
x
0
1
0
0
0
1
0
0
1
0
1
0
1
1
0
1
0
1
1
0
1
1
1
0
Bus Cycle Type
80C187 Not Selected
80C187 Not Selected
Opcode Write to 80C187
CW or SW Read from 80C187
Read Data from 80C187
Write Data to 80C187
Write Exception Pointers
Reserved
Read Opcode Status
Reserved
DATA INTERFACE AND CONTROL UNIT
The data interface and control unit latches the data
and subject to BCL control directs the data to the
FIFO or the instruction decoder The instruction de-
coder decodes the ESC instructions sent to it by the
CPU and generates controls that direct the data flow
in the FIFO It also triggers the microinstruction se-
quencer that controls execution of each instruction
If the ESC instruction is FINIT FCLEX FSTSW
FSTSW AX FSTCW FSETPM or FRSTPM the
control executes it independently of the FPU and the
sequencer The data interface and control unit is the
one that generates the BUSY PEREQ and ERROR
signals that synchronize 80C187 activities with the
CPU
FLOATING-POINT UNIT
The FPU executes all instructions that involve the
register stack including arithmetic logical transcen-
dental constant and data transfer instructions The
data path in the FPU is 84 bits wide (68 significant
bits 15 exponent bits and a sign bit) which allows
internal operand transfers to be performed at very
high speeds
Bus Cycles
The pins NPS1 NPS2 CMD0 CMD1 NPRD and
NPWR identify bus cycles for the NPX Table 10 de-
fines the types of 80C187 bus cycles
80C187 ADDRESSING
The NPS1 NPS2 CMD0 and CMD1 signals allow
the NPX to identify which bus cycles are intended for
the NPX The NPX responds to I O cycles when the
I O address is 00F8H 00FAH 00FCH or 00FEH
The correspondence betwen I O addresses and
control signals is defined by Table 11 To guarantee
correct operation of the NPX programs must not
perform any I O operations to these reserved port
addresses
I O Address
(Hexadecimal)
00F8
00FA
00FC
00FE
Table 11 I O Address Decoding
80C187 Select and Command Inputs
NPS2
NPS1
CMD1
1
0
0
1
0
0
1
0
1
1
0
1
CMD0
0
1
0
1
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