80C186EC/80C188EC Microprocessor User's Manual

CHAPTER 14
MATH COPROCESSING
The 80C186 Modular Core Family meets the need for a general-purpose embedded microprocessor.
In most data control applications, efficient data movement and control instructions are foremost
and arithmetic performed on the data is simple. However, some applications do require
more powerful arithmetic instructions and more complex data types than those provided by the
80C186 Modular Core.
14.1 OVERVIEW OF MATH COPROCESSING
Applications needing advanced mathematics capabilities have the following characteristics.
• Numeric data values are non-integral or vary over a wide range
• Algorithms produce very large or very small intermediate results
• Computations must be precise (i.e., calculations must retain several significant digits)
• Computations must be reliable without dependence on programmed algorithms
• Overall math performance exceeds that afforded by a general-purpose processor and
software alone
For the 80C186 Modular Core family, the 80C187 math coprocessor satisfies the need for powerful
mathematics. The 80C187 can increase the math performance of the microprocessor system
by 50 to 100 times.
14.2 AVAILABILITY OF MATH COPROCESSING
The 80C186 Modular Core supports the 80C187 with a hardware interface under microcode control.
However, not all proliferations support the 80C187. Some package types have insufficient
leads to support the required external handshaking requirements. The 3-volt versions of the processor
do not specify math coprocessing because the 80C187 has only a 5-volt rating. Please refer
to the current data sheets for details.
The core has an Escape Trap (ET) bit in the PCB Relocation Register (Figure 4-1 on page 4-2) to
control the availability of math coprocessing. If the ET bit is set, an attempted numerics execution
results in a Type 7 interrupt. The 80C187 will not work with the 8-bit bus version of the processor
because all 80C187 accesses must be 16-bit. The 80C188 Modular Core automatically traps ESC
(numerics) opcodes to the Type 7 interrupt, regardless of Relocation Register programming.
14-1