Appendix A. Hardware I/O Map

	I/O Map of XT Class Machines
Hex Address	Address Function in XT Class Machines
000-00F	DMA controller (8237A)
020-021	interrupt controller (8259A)
040-043	timer (8253)
060-063	PPI(8255A)
080-083	DMA page register (74LS612)
0A0-0AF	NMI - non maskable interrupt
200-20F	game port joystick controller
210-217	expansion unit
2E8-2EF	COM4 serial port
2F8-2FF	COM2 serial port
300-31F	prototype card
320-32F	hard disk
378-37F	parallel print
380-38F	SDLC
3B0-3BF	MDA - monochrome adapter and printer
3D0-3D7	CGA - color graphics adapter
3E8-3EF	COM3 serial port
3F0-3F7	floppy diskette controller
3F8-3FF	COM1 serial port

14	Documentation Number PCRTC2095 Manual
B&B Electronics --	PO Box 1040 -- Ottawa, IL 61350

PH (815) 433-5100 -- FAX (815) 433-5105

I/O Map of XT Class Machines