22-11-2012, 05:17 PM
Architecture of 8087
Architecture of 8087.pdf (Size: 264.91 KB / Downloads: 121)
Control Unit
Control unit: To synchronize the operation of the
coprocessor and the processor.
This unit has a Control word and Status word and Data
Buffer
If instruction is an ESCape (coprocessor) instruction,
the coprocessor executes it, if not the microprocessor
executes.
Status Register
TOP- Top of the stack (ST) bit indicates the current
register address as the top of the stack.
ES-Error summary bit is set if any unmasked error bit (PE,
UE, OE, ZE, DE, or IE) is set. In the 8087 the error
summary is also caused a coprocessor interrupt.
PE- Precision error indicates that the result or operand
executes selected precision.
UE-Under flow error indicates the result is too large to be
represent with the current precision selected by the control
word.
Status
Control Register
Control register selects precision, rounding control,
infinity control.
It also masks an unmasks the exception bits that
correspond to the rightmost Six bits of status register.
Instruction FLDCW is used to load the value into the
control register.
Numeric Execution Unit
This performs all operations that access and manipulate the
numeric data in the coprocessor’s registers.
Numeric registers in NUE are 80 bits wide.
NUE is able to perform arithmetic, logical and transcendental
operations as well as supply a small number of mathematical
constants from its on-chip ROM.
Numeric data is routed into two parts ways
a 64 bit mantissa bus and
a 16 bit sign/exponent bus.