8. To interface 8253 programmable interval timer to 8085 and verify the operation of 8253 in six different modes.

ORG 0000h  ; Starting address of the program

; Initialize the 8253

MOV AL, 00110110b  ; Load control word for timer 0 into AL (mode 3, binary counting, L-H byte access)

OUT 43h           ; Send control word to 8253

MOV AL, 11110100b  ; Load L-byte count (LSB) of 1000 into AL

OUT 40h           ; Send LSB of count to 8253

MOV AL, 00000100b  ; Load H-byte count (MSB) of 1000 into AL

OUT 40h           ; Send MSB of count to 8253

; Verify Mode 3 operation

IN AL, 40h         ; Read back L-byte count

MOV BL, AL         ; Save L-byte count in BL

IN AL, 40h         ; Read back H-byte count

MOV BH, AL         ; Save H-byte count in BH

HLT               ; End of program