8/12/2019 354 39 Solutions Instructor Manual 9 Introduction 8051 Microcontrollers Chapter 9

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Chapter9

Introductionto8051Microcontrollers

SolutionstoThinkandAnswerExercises1. Findthecontentsoftheflagsinthe8051afteraddingthebinarynumbers01011100B

and11000101B.

Resultis00100001BflagcontentsareP=0,OV=0,AC=1,andCY=1.

2. WritethebinarywordtobewrittenintothePSWofthe8051,toselecttheregisterbank2intheinternalRAM.

PSW CY AC F0 RS1 RS0 OV P

Bitaddress D7H D6H D5H D4H D3H D2H D1H D0HX X X 1 0 X X X

ThedatatobewrittentothePSWforselectingtheregisterbank2is(00010000B)or

10H.

3. Giveatleasttwoexamplesofsituationsinwhichtheoverflowflagisset.The conditions under which the OV flag is set after adding signed numbers are as

follows:

Positive+Positive=Negative

Negative+Negative=Positive

Positive Negative=Negative

Negative Positive=Positive

4. Whatdoesa0inthezeroflagmean,afteranarithmeticoperation?Azerointhezeroflagmeansthecontentoftheaccumulatorisallzero.

Microprocessors and Microcontrollers Kumar, Saravanan & Jeevananthan

Oxford University Press 2011