8255.Al8255A·5

CONTROL WORD

PC2~

1'"INPUT

o"'OUTPUT

'-----PORT B

1'" INPUT

0= OUTPUT

'-------GROUP 8 MODE 0" MODE ,0 1'"MODE 1

Figure 11. MODE Control Word

Figure 12. MODE 2

DATA FROM

/; CPU TO 8255A

/

INTR

IBF

I

1----""

--ltAOi-

PERIPHERAL _________ _

r ----

------t

BUS

DATA FROM

 

PERIPHERAL TO 8255A

 

 

DATA FROM

 

8255A TO 8080

Figure 13. MODE.2 (Bidirectional)

NOTE: Any sequence where WR occurs before ACK and STB occurs before RD is permissible. (lNTR = IBF·MASK· STB 'RD+OBF • MASK· ACK· WR)

9-28

AFN·OO744A·12

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Image 343
Intel mcs-48 manual 8255.Al8255A·5, LtAOi