80C186EB/80C188EB Microprocessor User's Manual - CEUNES

CHAPTER 12MATH COPROCESSINGThe 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 foremostand arithmetic performed on the data is simple. However, some applications do requiremore powerful arithmetic instructions and more complex data types than those provided by the80C186 Modular Core.12.1 OVERVIEW OF MATH COPROCESSINGApplications 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 andsoftware aloneFor the 80C186 Modular Core family, the 80C187 math coprocessor satisfies the need for powerfulmathematics. The 80C187 can increase the math performance of the microprocessor systemby 50 to 100 times.12.2 AVAILABILITY OF MATH COPROCESSINGThe 80C186 Modular Core supports the 80C187 with a hardware interface under microcode control.However, not all proliferations support the 80C187. Some package types have insufficientleads to support the required external handshaking requirements. The 3-volt versions of the processordo not specify math coprocessing because the 80C187 has only a 5-volt rating. Please referto 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) tocontrol the availability of math coprocessing. If the ET bit is set, an attempted numerics executionresults in a Type 7 interrupt. The 80C187 will not work with the 8-bit bus version of the processorbecause 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.12-1