CONTROL WORD D7 D6 DS D4 D3 D2 D1 DO CONTROL WORD GROUP E D7 D6 DS D4 D3 D2 D1 D

Question

CONTROL WORD D7 D6 DS D4 D3 D2 D1 DO CONTROL WORD GROUP E D7 D6 DS D4 D3 D2 D1 DO PORT C (LOWER) BIT SETIRESET OUTPUT PORT B 0 OUTPUT MODE SELECTION 1MODE 1 0 = RESET DON'T CARE BIT SELECT 01010101 BO 00110011 B1 00001111 B2 GROUPA PORT C (UPPER) 1 INPUT OUTPUT BIT SETIRESET FLAG 0= ACTIVE PORT A 1 INPUT 0OUTPUT MODE SELECTION 00 MODE 0 1 MODE 1 X MODE 2 MODE SET FLAG 1 Port 10 output using port I0 is - 39. The control word to configure 8255 PA, PB as input, PC as (d) 92H (b) 8DH (c) 83H (a) 12H

Explanation / Answer

D7 =1 = since set the IO Port

D6, D5 = X

D4= 1= Since port A has to be input

D3= 0 since port C has to be output

D2= 0 = Mode set flag

D1= 1= Since port B has to be input

D0= 0 since port C has to be output

THerefore the control word is 92H ( 1001 0010 )

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