Math Coprocessor Control; Figure 6-11: 36-Pin Expansion Bus I/O Channels - Datatech Enterprises Apex 386SX/20 User Manual

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 coproces-
sor 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
D C