Cau 20 Thiet bi giao dien vao ra song song

Y nghia cac tin hieu:

Tin hieu STROBE:dung de chot du lieu vao thiet bi ngoai vi hoac may in

Tin hieu AUTOFEED:dieu khien dich 1 dong in cua may in

Tin hieu xung INT: khoi dong may in

Tin hieu SELECT OUT:dung de "bat tay" voi thiet bi ngoai vi chon may in

Tin hieuERROR:bao may in dang trong trang thai co loi

Tin hieu SELECT IN bao may in da san sang lam viec

Tin hieu PE bao may in gap loi het giay

Tin hieuACK bao may in san sang nhan 1 ki tu moi

Tin hieu BUSY (=0) bao may in dang ban hoac khong ban

Y nghia cac thanh ghi:

Thanh ghi du lieu:chua du lieu xuat ra hoac du lieu nhap vao

Thanh ghi dieu khien:chua cac bit tao tin hieu bat tay voi thiet bi ngoai vi

Thanh ghi trang thai:chua cac bit thong tin phan anh trang thai cua cac tin hieu vao.

Trao doi thong tin giua 2 may tinh qua cong song song:

Khi 1 may tinh co tin hieu muontrao doi thong tin voi may tinh khac.no phat ra tin hieu SELECT OUT de bat tay voi may tinh khac.may tinh thu2 se phat ra tin hien SELECT IN de bao san sang lam viec.khi do o may tinh 1 tin hieu STROBE se dc phat di de chot du lieu muon gui di.va may tinh 2 phat ra tin hieu ACK san sang nhan du lieu moi.may tinh1 phat ra tin hieu INIT khoi dong qua trinh trao doi thong tin va may tinh 2 phat tin hieu BUSY bao lai trang thai ban hoac khong ban co the nhan hay khog nhan du lieu.