What is subroutine? What is the difference between CALL and JMP instructions?
Refer Section 4.6 and Section 3.5.4.
(a) How many ports are there in 8255 and what are they?
There are three eight-bit ports in 8255 such as Port A, Port B, and Port C.
(b) Discuss the different bits of the control word of 8255.
Refer Section 12.5.
(c)Write down the MODE-0 control word for the following:
(i) Port A = Input
(ii) Port B not used
(iii) Port C upper = Input, Port C lower = output.
The Control word Bits of 8255 is given below
When 8255 operate in mode 0, Port A as Input, Port C upper as Input, Port C lower as output and
Port B not used, the control word will be = 10011010 = 9AH as D0
= 1, D1
= 1 (assuming Port B
as input), D2
= 0, D3
= 1, D4
= 1, D5
D6
= 00 and D7
= 1.
(d) Discuss BSR operation of 8255.
Refer Section 12.4.4 and Fig. 12.14.