User Guide

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 [phone]
B&B Electronics Ltd – Westlink Comm. Pk – Oranmore, Galway, Ireland – Ph [phone] – Fax [phone]
Any eight-byte space not listed above or not used by any
other equipment in your system may be used by the WDT.
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