GIAO TIẾP NỐI TIẾP VI ĐIỀU KHIỂN 8051

I HC QUC GIA TP.H CH MINHTRNG I HC BCH KHOA

KHOA IN-IN T B MN K THUT IN T

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CHNG 3

H VI IU KHIN 8051

B mn K Thut in T - HBK

3.6 Cng ni tip (Serial Port)

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Ni dung

Gii thiu

Chun EIA(Electronic Industries Association)-232E hoc RS232

Giao tip cng ni tip MCS-51/52

ng dng ca ch 0

ng dng ca ch 1

ng dng ca ch 2 & 3

Cc th d.

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Truyn d liu ni tip

Truyn d liu khong cch xa Tc truyn d liu thp Truyn d liu ni tip ng b

Dng tn hiu clock ring ng b ha mch thu v pht.

Thng dng khung d liu ln hn v nhanh hn.

Truyn d liu ni tip bt ng b Khng cn tn hiu clock ring ng b ho chuyn

d liu. Da trn k{ t. Mi k{ t c ng khung bng start

bit v stop bit. Bn thu cn nhn dng start bit v stop bit nhn

ng k{ t d liu.

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Truyn d liu ni tip ng b (synchronous) v bt ng b (asynchronous) vi 8051

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ng truyn d liu c bn

Ngi ta c th s dng ng in thoi cng cng hoc dnh ring lm mi trng truyn d liu ni tip bt ng b.

Modem c dng chuyn i d liu s thnh dng sng analog thch hp cho vic truyn trn ng dy in thoi v ngc li.

C 2 kiu ng truyn: im n im v a im.

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DTE DCE DCE DTE

Computer or

terminal

Modem Modem Computer or

terminal

Communication linkDTE: Data Terminal EquipmentDCE: Data Communications Equipmnent


ng truyn im n im v a im

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Master

Slave 1 Slave 2 Slave n

Address 1 Address 2 Address n

Station Station

Peer Peer

Tx

TxRx

Rx


C bn v cc ng truyn

H thng 2 dy v 4 dy:

2 dy: tn hiu v t.

4 dy: 2 b 2 dy.

Cc kiu ng truyn:

n cng (Simplex link): ng dy dnh ring cho thu hoc pht ch khng c hai.

Bn song cng (Half-duplex link): ng dy c th dng cho pht hoc thu nhng mi ln ch c 1 chiu.

Song cng (Full-duplex link): Pht v thu c th tin hnh ng thi. ng truyn cn 4 dy.

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C bn v cc ng truyn

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5V

0V

>+3V


EIA-232-E or RS-232

EIA-232-E or RS-232 can apply to the following data communication schemes:

Serial communications

Synchronous and asynchronous

Dedicated leased or private lines

Switched service

Two wire or four wire

Point to point or multipoint

4 aspects in EIA-232-E interface: mechanical, functional, procedural, and electrical.

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EIA-232-E Mechanical Characteristics

25-pin DB25 /9-pin DB9 plug connector.

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DB-9 Signals

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Cng ni tip ca 8051

Cng ni tip ca 8051 c th hot ng trn mt di rng tn s

Chc nng:

Chuyn i song song ni tip khi xut

Chuyn i ni tip song song khi nhn

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S khi cng ni tip ca 8051

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Cc c tnh ca cng ni tip 8051

Song cng (ful-duplex)

C m khi thu (b m 1 byte): nu CPU c k t th nht trckhi k t th 2 c nhn y th d liu s khng b mt

C 4 ch lm vic (0 - 3)

Lp trnh d dng :

Chn tc (c nh (on-chip OSC/12 hoc OSC/64), hoc thay i c (T1))

Chn ch lm vic

Cho chy (SCON)

D s dng

Truyn d liu: MOV SBUF, A

Nhn d liu: MOV A, SBUF

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Thanh ghi iu khin cng ni tip SCON

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Cc ch hot ng ca cng ni tip

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Trc khi s dng cng ni tip, SCON c khi to tr vi ch ng, v v.v... Th d, cc lnh sau

MOV SCON, #01010010B

khi to tr cho cng ni tip ch 1 (SM0/SM1=0/1), cho php b thu (REN=1) v t c ngt pht (T1=1) ch b pht sn sng hot ng.


Ch 0:Thanh ghi dch 8 bit (1/3)

RXD l chn xut/nhp d liu

TXD l ng ra xung nhp dch

Tm bit c pht ra hay thu vo vi LSB i trc.

Tc baud c nh l 1/12 tn s mch dao ng trn chip

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Pht: c khi ng bng lnh ghi vo SBUF



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Vic thu: c khi ng khi bit cho php b thu REN = 1 v RI = 0


Ch 1: UART 8 bit c tc baud thayi c (1/3)

ch 1, 10 bit c pht i trn TXD hoc c thu vo RXD. Cc bit ny bao gm 1 bit bt u (lun lun l 0), 8 bit d liu (LSB i trc), v 1 bit dng (lun lun l 1).

hot ng b thu, bit dng i vo RB8 trong SCON. Trong 8051, tc baud c t bng tc trn ca Timer 1.

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Ch 1: UART 8 bit c tc baud thayi c (2/3)

Vic pht c khi ng bng cch ghi vo SBUF, nhng khng tht s bt u cho n khi cnh xung k ca b m chia 16 cung cp tc baud cng ni tip. D liu c dch ra trn ng TXD bt u bng bit bt u (start bit), theo sau l 8 bit d liu, v k n l bit dng. Chu kz ca mi bit l nghch o ca tc baud c lp trnh trong timer. C ngt pht (TI) c t ln 1 ngay khi bit dng xut hin trn TXD .

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s kin ng b ha


Ch 1: UART 8 bit c tc baud thay i c (3/3)

Vic thu c khi ng bi chuyn tip 1 sang 0 RXD. B m chia 16 creset tc thi ng chnh cc s m vi chui bit n. Chui bit n cly mu gia 16 ln m.

Gi s b thu pht hin bit bt u hp l th tip tc nhn k t. Bit bt uc b qua v 8 bit d liu c nhp vo thanh ghi dch cng ni tip. Khi ttc 8 bit c nhp vo th xy ra:

Bit th 9 (bit dng) c nhp vo RB8 trong SCON.

SBUF c np vi 8 bit d liu, v

C ngt ca b thu (RI) c t ln 1.

Tuy nhin cc iu trn ch xy ra nu c cc iu kin sau:

RI = 0, v

SM2 = 1, v bit dng nhn c = 1, hoc SM2=0.

Yu cu RI = 0 bo m rng phn mm c k t trc (v xa RI).iu kin th 2 th hi phc tp, nhng ch p dng trong ch truyn thnga x l. N hm { Khng c t RI ln 1 trong ch truyn thng a x lkhi bit d liu th chn l 0.

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Ch 2: UART 9 bit c tc baud c nh

Khi SM1 =0 v SM0 = 1, cng ni tip hot ng ch 2 nh UART 9 bit vi tc baud c nh. Mi mt bit c pht hoc thu: 1 bit bt u, 8 bit

d liu, 1 bit d liu th 9 lp trnh c, v 1 bit dng. Khi pht, bit th 9 l ni dung ca bit TB8 trong

SCON. Khi thu, bit th 9 thu c c t trong RB8. Tc baud ch 2 l 1/32 hay 1/64 tn s mch

dao ng trn chip (xem thm mc tc baud cngni tip).

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Ch 3: UART 9 bit c tc baud thay i c

Ch 3 ging vi ch 2 ngoi tr tc baud c lp trnh v c cung cp bi timer.

Tht ra cc ch 1, 2, v 3 rt ging nhau. Skhc bit l tc baud (c nh trong ch 2, thay i c trong ch 1 v 3) v s bit dliu (8 trong ch 1, 9 trong ch 2 v 3)

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Khi to tr v truy cp cc thanh ghi cng ni tip

Cc tc v vi cng ni tip

Cho php b thu

Truyn (thu/pht) d liu ni tip

Thm bit kim tra chn l

Cc c ngt

t tc baud cho cng ni tip

Truyn thng a x l

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S dng cc bit trong thanh ghi SCON

Cho php b thu (REN bit 4)

SETB REN Hoc

MOV SCON, #xxx1xxxxB ; vi x=0/1

Cc c ngt RI, TI: Cc c ny c bt ln bi phn cng nhng phi c xa bng phn mm.

RI = 1: B m nhn y; TI = 1: B m pht rng

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Cho php b thu Truyn d liu ni tip

1. Thu ni tip:

NHAN: JNB RI, $

CLR RI

MOV A, SBUF

RET

2. Pht ni tip:

PHAT: JNB TI, $

CLR TI

MOV SBUF,A

RET


bit kim tra chn l - TB8 kim tra chn/l (nu khng c dng (*) l chn)

; qua bit nh C

MOV C, P

CPL C ; kim tra l (*)

MOV TB8, C

MOV SBUF, A

; ch 1: 7-bit + 1 parity-bit

CLR ACC.7

MOV C, P

MOV ACC.7, C

MOV SBUF, A

Nu Parity lun lun bng 1 c 2 bit dng

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Thm bit kim tra chn l


t tc baud cho cng ni tip

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Cch t SMOD ln 1MOV A,PCON

SETB ACC.7

MOV PCON,A


S dng Timer 1 lm xung nhp tc baud

Khi to tr TMOD ch timer 8 bit t ng np li tr u (ch 2 ca timer) v t gi tr np li vo TH1 cho tc trn bng tc baud. TMOD c khi to tr nh sau:

MOVTMOD, #0010xxxxB

vi x c gi tr 0 hay 1 cn cho Timer 0.

t tc baud rt thp bng cch dng Timer 1 ch 16 bit , vi TMOD = #0001xxxxB. Tuy nhin phi khi to tr li cc thanh ghi TL1/TH1 sau mi ln trn. Vic ny s c thc hin trong chng trnh phc v ngt.

Mt la chn khc l cung cp xung nhp Timer1 bng xung nhp bn ngoi qua chn T1 (P3.5). Tc baud l 1/32 tc trn ca Timer 1.

Do cng thc xc nh tc baud trong cc ch 1 v 3 l

Tc baud = 1/32 Tc trn ca Timer 1

Th d: hot ng 1200 baud cn tc trn nh sau

1200 = 1/32 Tc trn ca Timer 1

Tc trn ca Timer 1 = 32 x 1200 = 38400 = 38.4 KHz -> Toverflow = 1/38.4 kHz = 26.04 s

Vi XTAL=12 MHz -> TCLK = 1 s. Overflow cn Toverflow/TCLK 26 clocks

Gi tr np cho timer 1 l -26

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Tm tt tc baud

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Th d 1: Khi to tr cho cng ni tip

Vit chui lnh khi to tr cng ni tip hot ng nh UART 8 bit vi tc 2400 baud. S dng Timer 1 cung cp xung nhp tc baud.

Bi gii.

Vi th d ny, c 4 thanh ghi phi c khi to tr l: SCON, TMOD, TCON, v TH1. Gi tr cn khi to tr cho cc thanh ghi nh sau

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ORG 8100H

INIT: MOV SCON, #52H

MOV TMOD, #20H

MOV TH1, #-13

SETB TR1

END


Th d 2: Gi s 10 byte chui d liu c lu trong RAM ni t a ch 30H. Vit

chng trnh gi chui d liu ny n cng ni tip ca 8051 (1200 baud, crystal 11.0592 MHz)

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ORG 0000H

MOV SCON,#01010010B ;Serial port mode 1

MOV TMOD,#00100000B ;Timer 1 mode 2

MOV TH1,#-24 ;reload count for 1200 baud

SETB TR1 ;start Timer 1

MOV R2,#10 ;number of loops

MOV R0,#30H ;starting address

LOOP: MOV A,@R0 ;get data

ACALL SEND ;send data

INC R0 ;increase pointer

DJNZ R2,LOOP ;loop 10 times

SJMP DONE

SEND: JNB TI,$ ;transmit buffer empty? No:check again

CLR TI ;yes: clear flag and

MOV SBUF,A ; send data

RET ;return

DONE: NOP

END


Th d 3

Gi s chui d liu c lu trong RAM ni t a ch 30H n 50H. Vit chng trnh gi chui d liu ny ra cng ni tip 8051 dng UART 8-bit, 2400 baud, 11.059-MHz crystal

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ORG 0000H

MOV SCON,#01010010B

MOV TMOD,#00100000B

MOV TH1,#-12

SETB TR1

MOV R0,#30H

LOOP: MOV A,@R0

ACALL SEND

INC R0

CJNE R0,#51H,LOOP

SJMP DONE

SEND: JNB TI,$

CLR TI

MOV SBUF,A

RET

DONE: NOP

END


Th d 4 Vit chng trnh nhn 20-byte chui d liu t cng ni tip dng UART 8-

bit, 2400 baud, 11.059-MHz crystal v ghi vo RAM ni bt u t a ch 40H

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ORG 0000H







LOOP: ACALL RECEIVE ;receive data

MOV @R0,A ;store data



SJMP DONE

RECEIVE:

JNB RI,$ ;receive buffer full? No: check again

CLR RI ;yes: clear flag and

MOV A,SBUF ; receive data

RET ;return

DONE: NOP

END


Th d 5 Vit chng trnh nhn 40-byte chui d liu t cng ni tip dng UART 8-

bit, 4800 baud, 11.059-MHz crystal v ghi vo RAM ni bt u t a ch 40H

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ORG 0000H








MOV @R0,A ;store data



SJMP DONE

RECEIVE:



MOV A,SBUF ; receive data

RET ;return

DONE: NOP

END


Th d 6: Chng trnh xut k t

Vit chng trnh con OUTCHR pht m ASCII 7 bit trong thanh ghi tch ly A ra cng nitip ca 8051 vi bit kim tra l c thm vo nh bit th 8. Tr v t chng trnh con khng lm thay i tr ca thanh ghi tch ly trc khi gi chng trnh con.

Bi gii.

Th d ny v th d k minh ha 2 trong s cc chng trnh con thng dng nht trn cc h vi tnh c gn thit b u cui RS232: xut k{ t (OUTCHR) v nhp k{ t (INCHAR).

OUTCHR: MOV C, P ; t bit kim ra chn vo c C

CPL C ; i sang kim tra l

MOV ACC.7, C ; thm vo m k{ t

AGAIN: JNB TI, AGAIN ; TX c rnh ? Khng : kim tra li

CLR TI ; Truyn c xa c TI v

MOV SBUF, A ; gi k{ t

CLR ACC.7 ; b bit kim tra l v

RET ; quay v

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Th d, cc lnh sau pht m ASCII cho ch Z n thit b ni tip gn vo cng ni tip ca 8051:

MOV A, # Z

CALL OUTCHR

(tip tc)

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Th d 7: Chng trnh con nhp k t

Vit chng trnh con INCHAR nhp 1 k t t cng ni tip ca8051 v tr v vi m ASCII 7 bit trong thanh ghi tch ly. Bit kimtra l c t trong bit th 8 nhn c v t c nh ln 1 nuc sai v kim tra chn l.

INCHAR: JNB RI, $ ; i k t

CLR RI ; xa c

MOV A, SBUF ; c k t vo A

MOV C, P ; vi kim tra l trong A, P s = 1

CPL C ; b ch c li

CLR ACC.7 ; b bit kim tra chn l

RET

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Th d 8

Gi s 10-byte chui d liu ASCII 8-bit c lu trong RAM ni t a ch 30H. Vit chng trnh pht chui d liu ny ra cng ni tip (4800 baud, crystal 11.0592 MHz) vi c kim tra l c truyn nh bit th 9.

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Th d 8

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ORG 0000H

MOV SCON,#11010010B ;Serial port mode 3 (9-bit)






LOOP: MOV A,@R0 ;get data

MOV C,P ;put even parity bit in C flag

CPL C ;convert to odd parity

MOV TB8,C ;and move to the 9th data bit

ACALL SEND ;send data



SJMP DONE

SEND: JNB TI,$ ;check TI empty? No: check again

CLR TI ;yes: clear flag and

MOV SBUF,A ; send data

RET ;return

DONE: NOP

END


Th d 9 Vit chng trnh nhn 40-byte chui d liu t cng ni tip dng UART 8-bit, 4800

baud, 11.059-MHz crystal v ghi ra RAM ngoi bt u t a ch 5000H

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ORG 0000H






MOV DPTR,#5000H ;starting address


MOVX @DPTR,A ;store data

INC DPTR ;increase pointer


SJMP DONE

RECEIVE:



MOV A,SBUF ;receive data

RET ;return

DONE: NOP

END


Exercise

Vit chng trnh nhn 50-byte chui d liu t cng ni tip dng UART 8-bit, 2400 bps, 11.059 MHz v kim tra: Nu byte d liu l s chn th ghi vo RAM ni bt u t a ch 40H

Nu byte d liu l s l th ghi ra RAM ngoi bt u t a ch 2000H

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Ti liu tham kho

H Trung M, Vi x l{, Nh xut bn i hc Quc Gia Tp. HCM - 2003

I. Scott MacKenzie , The 8051 Microcontroller, 2nd Edition, Prentice-Hall, 1995

Slide bi ging thy H Trung M

Slide bi ging thy L Ch Thng.

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GIAO TIẾP NỐI TIẾP VI ĐIỀU KHIỂN 8051

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