t -RS422-RS485 RS232, RS485 v RS422 ch yu l n n m tn hi u n c trn u khin, t u n t , t l tn hi u, cc cp n p, ngn mch hnh vi, ti t n sut v n p chu c cc cp. N n c mt s khc bi t gi a m n i trong s h. Bt k k s oc chuyn gia v truyn thng d li u n t c th phn bi t gi a RS232, RS485 v RS422 d dn n n n c th n c d dng cho tt c. i vi h, s khc bi t gi c cho gia nhp d y. 1. RS232 l chun lu i nht ca Hi p hi Cng nghi p n t (EIA) c theo sau bi RS422 v RS485. Ngun gc ca RS232 c th c truy tr li nh n n y y u n t x c kt ni vi khung chnh thng qua modem. Truyn thng gi a DCE (Data Circuit-chm dt thit b) v DTE (D t Ter n l Equ p ent) c s dn xy ra tun t . Ton b qu trnh rt chm v rt c. Vi s p c , EIA c th c hi n mt tiu chun m gim thiu s n tn t lm cho cuc sng d dn n o n n n i tham gia vi cc b phn cng ngh thng tin v truyn thng d li u. N n thiu st v hn ch v t , ki so t lu ln v tin cy t ra mt cu hi v hi u sut c . y l n n RS422 RS422 cung cp mt gii php cho vn ny bng cch s dng hai b t u c v tch c c c n p. RS422 c t ln ti 10 megabit / giy vi mt khong cch kt ni khong 4.000 feet. 2. RS422 c hai cp xon n n p tiu c c v tch c c p n giao tip trong c ng cng mt l . Tron trng hp ca RS232, giao tip sau khi c mt n . 4 un p truyn d li u bng cch s dng phn hoc cn bng tn hi u. N ng dy truyn ti v khng th o n c unidirectional. Khng gin n EIA 485, n o p p n u n i nhn n n n n u trn u khin. N c li th l t u p n, u khin phn v d li u gi cao (10 megabaud ti 12 mt). EIA 422 mt khc ch x n c tnh c n tn hi u ca mt tn hi u cn bng duy nht. 485 n s dng cp xon ca chnh l n p tiu c c v tch c n n i vi giao tip ni tip d li u nh p n. u ny n c gi l EIA-485, TIA 485 b v u ny c xut bn bi ANSI Thng tin Hi p hi Cng nghi p (TIA) v Lin minh Cng nghi p n t (EIA). Chng c th c s dng c hi u qu trn mt khon d v tron trng vi ting n n. Nhiu n i nhn c th c kt ni vi cc trong mt cu hnh multi-drop. 3 RS232 v. RS422 l cc giao th n n n 32. Tuy nhin, RS 485 cng trnh gn n 4 tron 485 t t b a ch v c kh nn vn v t v khong cch. o t p vi nhiu nt, ln

4. RS485 l thch hp cho nhiu loi ch hay n l cc kt ni mng v kin trc. M n i trong s h c th kt ni bid re t on lly n dn m dt i ph xe xt c bi t. Tuy n n, n v 4 l m t m, h khng thch hp cho m ny. 5. N 4 t m u khin duy nht, n khng th c tt, n n EIA 485 o cu ph t trong ch truyn ti bn t mt tn hi u cho li xe. trn u khin 485 c yu