D CFigure 6-11: 36-Pin Expansion Bus I/O ChannelsMath Coprocessor ControlThe math coprocessor functions as an I/O device through I/O portaddresses hex 0F8, 0FA and 0FC. The microprocessor sends OPcodes and operands to I/O ports. The microprocessor also receivesand stores results through the same I/O ports. The “busy” signal sentby the processor forces the microprocessor to wait until the coproces-sor is finished executing.The following describes the math coprocessor controls:OF0The latched math coprocessor busy signal can be cleared with an 8-bit“out” command to port F0. The coprocessor will latch “busy” if it assertsits error signal. Data output should be zero.OF1The math coprocessor will reset if an 8-bit “out” command is sent toport F1. Again, the data output should be zero.24 Chapter 6: Appendix
