B&B Electronics ATRWDT, ATXWDT manual

	I/O Map of AT Class Machines
Hex Address	Address Function in AT Class Machine
000-01F	DMA controller #1 (8237A-5)
020-03F	Interrupt controller #1 (8259A)
040-05F	timer (8254)
060-06F	Keyboard (8042)
070-07F	NMI – non maskable interrupt & CMOS RAM
080-09F	DMA page register (74LS612)
0A0-0BF	Interrupt controller #2 (8259A)
0C0-0DF	DMA controller #2 (8237A)
0F0-0FF	80287 math coprocessor
1F0-1F8	hard disk
200-20F	game port joystick controller
258-25F	Intel Above Board
278-27F	parallel printer port 2
2E8-2EF	COM4 serial port
2F8-2FF	COM2 serial port
300-31F	Prototype card
378-37F	parallel printer 1
380-38F	SDLC or bisynch com 2
3A0-3AF	bisynch com 1
3B0-3BF	MDA – monochrome adapter
3BC-3BE	parallel printer on monochrome adapter
3C0-3CF	EGA – reserved
3D0-3D7	CGA – color graphics adapter
3E8-3EF	COM 3 serial port
3F0-3F7	floppy diskette controller
3F8-3FF	COM1 serial port

Any eight-byte space not listed above or not used by any other equipment in your system may be used by the WDT.

A-2 Appendix A Documentation Number ATxWDT-1303

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