Epson Apex 386SX/20 Canadian Product User Manual - Page 122
Math Cprocessor Control
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D C Figure 6-11: 36-Pin Expansion Bus I/O Channels Math Coprocessor Control The math coprocessor functions as an I/O device through I/O port addresses hex 0F8, 0FA and 0FC. The microprocessor sends OP codes and operands to I/O ports. The microprocessor also receives and stores results through the same I/O ports. The "busy" signal sent by the processor forces the microprocessor to wait until the coprocessor is finished executing. The following describes the math coprocessor controls: OF0 The latched math coprocessor busy signal can be cleared with an 8-bit "out" command to port F0. The coprocessor will latch "busy" if it asserts its error signal. Data output should be zero. OF1 The math coprocessor will reset if an 8-bit "out" command is sent to port F1. Again, the data output should be zero. 24 Chapter 6: Appendix