ii

Programming the DM5806 .................................................................................................................................... 4-7

Clearing and Setting Bits in a Port .................................................................................................................... 4-8

Initializing the 8255 PPI .................................................................................................................................... 4-9

Digital I/O Operations ....................................................................................................................................... 4-9

Timer/Counters .................................................................................................................................................. 4-9

Interrupts .......................................................................................................................................................... 4-11

What Is an Interrupt? ................................................................................................................................... 4-11

Interrupt Request Lines ............................................................................................................................... 4-11

8259 Programmable Interrupt Controller .................................................................................................... 4-11

Interrupt Mask Register (IMR) .................................................................................................................... 4-11

End-of-Interrupt (EOI) Command .............................................................................................................. 4-11

What Exactly Happens When an Interrupt Occurs? ................................................................................... 4-11

Using Interrupts in Your Programs ............................................................................................................. 4-12

Writing an Interrupt Service Routine (ISR) ................................................................................................ 4-12

Saving the Startup Interrupt Mask Register (IMR) and Interrupt Vector ................................................... 4-13

Restoring the Startup IMR and Interrupt Vector ......................................................................................... 4-14

Common Interrupt Mistakes ........................................................................................................................ 4-14

Example Programs ............................................................................................................................................... 4-14

C and Pascal Programs .................................................................................................................................... 4-14

BASIC Programs ............................................................................................................................................. 4-14

APPENDIX A — DM5806 SPECIFICATIONS .................................................................................. A-1

APPENDIX B — I/O CONNECTOR PIN ASSIGNMENTS ............................................................. B-1

APPENDIX C — COMPONENT DATA SHEETS ............................................................................. C-1

APPENDIX D — WARRANTY ............................................................................................................ D-1