B&B Electronics ATXWDT, ATRWDT manual Appendix A Hardware I/O Maps

Appendix A: Hardware I/O Maps

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

Documentation Number ATxWDT-1303 Appendix A A-1

B&B Electronics Mfg Co – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 B&B Electronics Ltd – Westlink Comm. Pk – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445