TRNG I HC BCH KHOA H NI VIN IN T VIN THNG

BO CO BI TP LN MN K THUT VI X L ti: Thit k Qut thng minh dng PIC16F877AGing vin hng dn: Nhm sinh vin: H v tn 1. Cao Vn Huy 2. Nguyn Thanh Tng 3. Khut Minh Phc 4. Lng Vn Hun 5. Phm Tun Anh TS. Phm Ngc Nam TC201-Group10 Lp T1-K54 T4-K54 T4-K54 T8-K54 T8-K54 SHSV 20091217 20093132 20092028 20091211 20090144

H Ni, 04 - 2012N Nhn xt ca ging vin hng dn

H Ni, Ngy Thng Ging Vin hng dn (K ghi r h tn)

Nm 2012

Nhn xt ca ging vin chm H Ni, Ngy Thng Ging Vin chm (K ghi r h tn) Nm 2012

Mc Lc

Li m uTrong thp nin cui th k 20, k thut in t lin tc c nhng tin b vt bc, c bit l trong k thut ch to vi mch in t. S ra i v pht trin nhanh chng ca k thut in t m c trng l k thut vi x l to mt bc ngot quan trng trong s pht trin khoa hc ngy nay, n nh hng quyt nh n con ng tin hc ha.

Nm 1970, cng ty Intel cho ra i b vi x l u tin c tn l Intel-4004, nhm p ng nhu cu cn thit ca mt cng ty kinh doanh l hng truyn thng BUSICOM. Intel-4004 l kt qu ca mt tng quan trng trong s pht trin k thut vi x l. Do kh nng mm do ha trong cc thao tc ca mnh, nm 1970 Intel-4004 tr thnh vi x l u tin trn th gii. Nm 1972, hng Intel cho ra i b vi x l 8088. Vn ch to theo cng ngh PMOS nhng l loi 8 bits. n y hng lot cc hng in t ni ting hng u th gii nh National, Rockwell, nhanh chng i vo sn xut v ch to cc b vi x l.

Nm 1974, Hng Intel cho ra i b vi x l 8080 - 8 bt song song c ch tp theo cng ngh NMOS nh du mt bc tin ln trn con ng lm ch tc x l tin ca k thut in t hin i. Cc hng khc cng cho ra i b vi x l tng ng nh 6800( Motorola), 8080( Texas Intrusment),

Ngy nay, nhng ng dng ca vi iu khin i su vo i sng sinh hot v sn xut ca con ngi, l mt phn tt yu khng th thiu trong i sng hin i. Th k 21 c xem l th k ca khoa hc cng ngh, l th k m my mc c thit k v lp trnh mt cch t ng thay th hot ng ca con

ngi trong sn xut, cng nh phc v cc cng vic trong sinh hot. Trong cuc sng mang tnh t ng ha cao th cc vi x l nh l mt cng c c lc h tr cho con ngi thc hin nhu cu ngy cng cao v cng hon thin ca mnh.

ang l sinh vin ngi trn gh nh trng, c hi tip cn, hc tp nhng cng ngh tin tin, hin i cha nhiu, nn trong qu trnh t hc v nghin cu, chng em c gng tm hiu v b vi x l, cng nh cc ng dng ca n, c bit l vi x l PIC16F877A. Vi nhng g nghin cu c nhm chng em lm thc hnh ng dng thng qua vic thit k qut thng minh. y l c hi rt ln cho chng em trau di kin thc thc t, p dng l thuyt hc v rn luyn bn thn trong mi trng lm vic nhm.

Do thi gian thc hin v kin thc cn hn ch nn cn nhiu sai st trong qu trnh thc hin ti, rt mong c s b sung ng gp ca cc thy c v cc bn.

Chng em xin chn trng cm n thy TS. Phm Ngc Nam v anh V Hu Tip nhit tnh hng dn chng em sut qu trnh hc tp.

Chng 1. T VN V KHO ST H THNG1.1. Kho st v phn tch h thngng dng ti: Ngy nay, khi cng ngh pht trin, con ngi i hi them nhiu thit b thng minh hn nhm phc v ti a cho cuc sng. Ni u cng s xut hin nhng nh my, khu cng nghip, cng ngh thng tin v k thut hin i cng gip cuc sng con ngi tr nn tt p v thoi mi hn. Vi s bng n ca k thut hin nay, th thit b thng minh i vi chng ta khng cn xa l na. ti hm nay chng ti mun gii thiu l: Qut thng minh. S khng cn phi qut nan hay qut tay khi m c in, s khng phi bt tp nng hay nt bm qut to hay nh, s khng phi thc gic khi cm thy lnh. Tt c cc vn trn s c a ra v gii quyt bi mt thit b thng minh m chng ti hy vng n s mang li rt nhiu li ch cho cuc sng con ngi: Qut thng minh

Qut thng minh (Smart Fan) c ng dng lm mt cho h thng mch in t, m rng ra n c th ng dng lm mt cho cc vn phng, cng ty, cc xng sn xut.

S tng qut h thng:

Khi thi gian thc (DS1307)

Khi o nhit (LM35)

Khi hin th (LCD, LED)

Vi x l Pic16f877a Khi ngun ng c

Cc thng s h thng v cc phm bm

1.2.

Gii thch s khi:

- Vi x l pic16f877a iu khin ton b h thng, thu nhn d liu t khi thi gian thc, khi o nhit , cc tn hiu t phm bm ri x l v a ra tn hiu iu khin cho cc khi hin th v ng c, hoc thit lp li gi tr cho khi thi gian thc - Khi thi gian thc: dng IC thi gian thc DS1307, lu tr v cp nht thi gian thc, vi x l i chiu vi thi gian c thit lp sn a ra cc tn hiu iu khin.

- Khi o nhit : mch s dng sensor LM35, khi c chc nng ly tn hiu nhit t mi trng ri a tn hiu vo vi iu khin chuyn i thnh nhit . - Khi hin th: gm c: LCD ,LED 7 thanh, v 1 n led. LCD dng hin th ngy gi thc, cc thng s trong qu trnh ci t. 2 LED 7 thanh dng hin th nhit mi trng hin ti. n led bo hiu tnh trng hot ng ca mch: sng: ang hot ng, khng sng : mch khng hot ng hoc ang trong ch ngh. - Khi ng c: l mt chic qut in dng lm mt h thng. - Khi bn phm: gm c 5 nt bm : menu, up,down, set, reset. Chc nng chung ca khi l gi n vi iu khin cc tn hiu nhm thit lp cc thng s cn thit cho h thng. Menu: Bt ch iu chnh , chuyn i iu chnh cc thng s v thot khi ch iu chnh. Cc ch cn iu chnh: gi, pht h thng => nhit cho php hot ng thp nht, cao nht => nhit l tng => gi pht bo dng => thi gian cao nht qut quay lin tc => thi gian ch cho ln chy tip theo. Khi n menu th ln lt i qua cc ch v dng phm up ( down) tng ( gim) thng s, khi iu chnh xong cn n nt set lu li. khi ht cc ch , n menu mt ln na th v ch ch ban u.

Up, down: dng tng hoc gim gi tr ca cc thng s ch iu chnh. V cc thng s c iu chnh kiu quay vng.

Set: sau khi iu chnh cc thng s cn n nt ny lu li. Reset: a cc thng s ca mch v ch mc nh. - Khi ngun: c nhim v cung cp nng lng hot ng cho ton mch. 1.3.-

M t hot ng ca h thng: Khi cp ngun cho ton h thng: khi cm bin thu tn hiu cho vi iu khin x l v hin th ln 2 led 7 thanh. Vi x l ly thi gian thc c lu trong DS1307 v thc hin hin th ln LCD

- Cc thng s c vi x l kim tra v nu tha mn ht th vi iu khin a ra tn hiu cho qut hot ng. - Nu nhit qu gii hn cho php l 60 , th vi x l thc hin cho qut hot ng. V iu chnh tc theo tham s nhit ca mi trng. Khi nhit h thng gim xung 50 tr xung, th qut s c iu khin tt. nu nhit sau 45m m vn trong khong 45->70 th h thng t ng bo dng. sau 10m li tip tc hot ng. - ch ch , LCD hin th ngy gi thc. khi n menu th n hin th ln lt cc thng s mc nh ca tng ch thc hin ci t. Cc thng s hin th ln lt trn LCD:-

Khi n up down, cc thng s s thay i trc tip trn LCD. Khi n set th LCD hin th ch : Setup done!. V cc thng s c lu

thay i vo vi x l. Khi n nt reset th ton b cc thng s ca h thng s v gi tr mc nh v LCD hin th dng ch : Reset done! - Nu c in cung cp cho h thng th n led s sng.

CHNG 2: PHN TCH YU CU2.1. Yu cu v chc nng

- Mch thc hin ng yu cu mong mun - Hin th gi, pht, ngy, thng, nm, trn LCD - Hin th nhit ln LED 7 thanh - S dng nt bm ci t thi gian - T ng iu chnh tc qut khi nhit thay i 2.2. Yu cu phi chc nng

- S dng vi iu khin PIC16F877A - Thit k mch nh hn 1dm2-

Thi gian thc hin ti 13 tun Mc tiu thit k

2.3.

- S dng IC cm bin nhit LM35 o nhit phng

- S dng IC thi gian thc DS1307 lu thi gian - S dng nt bm iu chnh thi gian - Tc qut thay i khi nhit phng thay i

2.4. K hoch thc hinSau khi phn tch h thng, v kh nng nhm pht trin cng nh qu trnh vn hnh h thng. K hoch c th thc hin theo trnh t

Tn qu trnh Nghin cu s b Phn tch Lp trnh, m phng V schematic layout t mch in Hn mch in v lm bo co

Thi gian 1 tun 3 tun 2 tun 1 tun 2 tun 1.5 tun 2.5 tun

Bt u 13/02/2012 20/02/2012 05/03/2012 19/03/2012 26/03/2012 09/04/2012 20/04/2012

Hon thnh 19/02/2012 11/03/2012 18/03/2012 25/03/2012 09/04/2012 19/04/2012 06/05/2012

Chng 3: PHN TCH KIN TRC H THNGH thng gm 8 khi chnh - Vi x l trung tm PIC16F877A - Khi ngun - Khi mch np - Khi led 7 thanh - Khi cm bin nhit - Khi hin th LCD - Khi giao tip DS1307-

Khi nt bm.

3.1.

Vi x l trung tm PIC16F877A:

3.1.1. S chn v s nguyn l ca PIC16F877A: 3.1.1.1. S chn:

3.1.1.2. S nguyn l:

3.1.2. Nhn xt: T s chn v s nguyn l nh trn, chng ta c th rt ra cc nhn xt nh sau: - PIC16F877A c tng cng 40 chn. - Bao gm 5 PORT, 2 chn cp ngun, 2 chn GND, 2 chn thch anh v 1 chn dng RESET vi iu khin. - 5 PORT ca PIC16F877A bao gm: PORT B: 8 chn

PORT D: 8 chn

PORT C: 8 chn

PORT A: 6 chn PORT E: 3 chn 3.1.3. Khi qut v chc nng ca cc port trong vi iu khin PIC16F877A: 3.1.3.1. PORT A: PORT A gm c 6 chn, cc chn ca port A c th lp trnh thc hin c 2 chc nng hai chiu : xut d liu t vi iu khin ra ngoi vi v nhp d liu t ngoi vi vo vi iu khin. Vic xut nhp d liu PIC16F877A khc vi h 8051, tt c cc port ca PIC16F877A, mi thi im ch thc hin mt chc nng xut hoc nhp. chuyn t chc nng ny sang chc nng xut hay nhp ngc li, ta phi x l bng phn mm, khng nh 8051 t hiu lc no l chc nng nhp, lc no l chc nng xut. Trong kin trc phn cng ca PIC16F877A, ngi ta s dng thanh ghi TRISA a ch 85H iu khin chc nng I/O trn. Mun xc lp cc chn no ca PORT A l nhp (input) th ta set bit tng ng chn trong thanh ghi TRISA. Ngc li, mun chn no l output th ta clear bit tng ng chn trong thanh ghi TRISA. iu ny hon ton tng t i vi cc PORT cn li Ngoi ra, PORT A cn c cc chc nng quan trng sau: - Ng vo Analog ca b ADC: thc hin chc nng chuyn t Analog sang Digital - Ng vo in th so snh. - Ng vo xung Clock ca Timer0 trong kin trc phn cng: thc hin cc nhim v m xung thng qua Timer0

- Ng vo ca b giao tip MSSP (Master Synchronous Serial Port) 3.1.3.2. PORT B: PORT B c 8 chn, cng nh PORT A, cc chn ca PORT B cng thc hin c 2 chc nng: input v output. Hai chc nng trn c iu khin bi thanh ghi TRISB. Khi mun chn no ca PORT B l input th set bit tng ng trong thanh ghi TRISB, ngc li mun chn no l output th clear bit tng ng trong TRISB. Thanh ghi TRISB cn c tch hp b in tre ko ln c th iu khin c bng chng trnh. 3.1.3.3. PORT C: PORT C c 8 chn v cng thc hin c 2 chc nng input v output di s iu khin ca thanh ghi TRISC tng t nh 2 thanh ghi trn. Ngoi ra PORT C cn c cc chc nng quan trng sau: - Ng vo xung Clock cho Timer1 trong kin trc phn cng - B PWM thc hin chc nng iu xung lp trnh c tn s, duty cycle: s dng trong iu khin tc v v tr ca ng c - Tch hp cc b giao tip ni tip I2C, SPI, SSP, US ART 3.1.3.4. PORT D: PORT D c 8 chn, thanh ghi TRISD iu khin 2 chc nng input v output ca port tng t nh trn. PORT D cng l cng xut d liu ca chun giao tip song song PSP (Parallel Slave Port). 3.1.3.5. PORT E:

PORT E c 3 chn, thanh ghi iu khin xut nhp tng ng l TRISE. Cc chn a PORT E c ng vo analog, bn cnh PORT E cn l cc chn iu khin ca chun giao tip PSP. 3.1.4. Ti sao s dng PIC16F877A m khng s dng 8051 cho ti ny: Trong chng trnh o to, chng em c hc v rt kinh nghim nhiu trn vi iu khin 8051. H vi iu khin 8051 l mt h vi iu khin in hnh, ph bin, d s dng, v lp trnh, rt ph hp vi sinh vin mi bt u lm quen n lp trnh cho vi iu khin thuc h 8051 (in hnh l 89C51, 89052), tuy nhin, do nhn ra cc nhc im c bn sau: - B nh Ram ni c dung lng thp, ch c 128 bytes. iu ny gay tr ngi ln khi thc hin cc d n ln vi vi iu khin 8051. khc phc ta phi m rng them lm hn ch s chn dnh cho cc ng dingj ca vi iu khin.-

S lng cc b giao tip ngoi vi tch hp sn trong 8051 t, khng c cc b ADC, PWM, truyn d liu song song. Khi mun s dng cc chc nng ny, ta phi s dng them cc IC bn ngoi, gy tn km v kh thc hin v d b nhiu nu khng bit cch chng nhiu tt.

- Ngoi ra cn mt s hn ch khc nhau nh s lng Timer ca 8051 t, ch c 2 Timer. Chnh iu ny lm cho gii thut khi vit chng trnh gp kh khn. Nhng nhc im cn bn trn ca 8051 cng nh yu cu ca ti, khin chng em a n quyt nh dng vi iu khin PIC16F877A gii quyt nhng vn t ra ca ti.

Vi k vng da trn nn tng kin thc tip thu c khi hc vi iu khin 8051, chng em rt mun t tm hiu mt h vi iukhin mi, mnh hn, p ng c nhiu yu cu hn, sau na l cho cc d n trong tng lai nu chng em c dp s dng vi iu khin trong d n ca mnh. Trong qu trnh tm hiu mt h vi iu khin mi tha mn yu cu nh em trnh by trn. Em thy PIC16F877A l mt la chn l tng. Ch cn xem xt qua cc port v chc nng ca port m em trnh by trn, ta cng d nhn ra nhng u im vt tri so vi vi iu khin 8051. Gi ca PIC16F877A trn th trng cng t gp 2 ln mt chip h 8051. S dng PIC16F877A trong ti ny c th l lng ph, nhng vi mc ch nng cao kh nng t tm ti v hc hi, phc v mc ch lu di sau ny, th y l mt s la chn chnh xc. l l do em chn dng PIC16F877A cho ti ny. 3.1.5. Tm hiu v PIC16F877A: 3.1.5.1. Cu trc phn cng ca PIC16F877A: PIC16F877A l dng PIC kh ph bin, kh y nhng tnh nng phc v cho hu ht tt c cc ng dng th t. y l dng PIC kh d cho ngi mi lm quen vi PIC, c th hc tp v to nn tng v h vi iu khin PIC ca mnh. Cu trc tng qut: - 8K Flash Rom - 368 bytes Ram - 256 bytes EFPROM

- 5 port vo ra vi tn hiu iu khin c lp - 2 b nh thi Timer0 v Timer2 8 bit - 1 b nh thi Timer1 16 bit c th hot ng c ch tit kim in nng vi ngun xung clock ngoi - 2 b Capture/Compare/PWM - 1 b bin i Analog -> Digital 10bit, 8 ng vo - 2 b so snh tng t - 1 b nh thi gim st (watch dog timer) - 1 cng song song 8 bit vi cc tn hiu iu khin - 1 cng ni tip - 15 ngun tt.

3.1.5.2. T chc b nh PIC16F877A: 3.1.5.2.1. B nh chng trnh:

B nh chng trnh ca PIC16F877A l b nh Flash, dung lng 8K word (1 word cha 14 bit) v c phn thnh nhiu tranh nh hnh trn. m ha c a ch 8K word b nh chng trnh, thanh ghi m chng trnh PC c dung lng 13 bit. Khi vi iu khin reset, b m chng trnh s tr v a ch 0000h. Khi c ngt xy ra th thanh ghi PC s tr n a ch 0004h.

B nh chng trnh khng bao gm b nh Stack v khng c a ch ha bi b m chng trnh. 3.1.5.2.2. B nh d liu: B nh d liu ca PIC16F877A c chia thnh 4 bank, mi bank c dung lng 128 byte. Mi bank ca b nh d liu PIC16F877A bao gm c cc thanh ghi c chc nng c bit SFR nm cc nh a ch thp v cc thanh ghi mc ch dng cung GPR nm vng a ch cn li ca mi bank thanh ghi. Vng nh cc thanh ghi mc ch dng chung ny chnh l ni ngi dng s lu d liu trong qu trnh vit chng trnh. Tt c cc bin d liu nn c khai bo cha trong vng a ch ny. Trong cu trc b d liu ca PIC16F877A, cc thanh ghi SFR no m thng xuyn c s dng ( nh thanh ghi STATUS) s c t tt c cc bank thun tin trong vic truy xut. S d nh vy l v, truy xut mt thanh ghi no trong b nh ca PIC16F877A ta cn phi khai bo ng bank cha thanh ghi , vic t cc thanh ghi s dng thng xuyn gip ta thun tin hn rt nhiu trong qua trnh truy xut, lm gim lnh chng trnh.

Da trn s 4 bank b nh d liu PIC16F877A t rt ra cc nhn xt sau:-

Bank0 gm cc nh c a ch t 00h n 77h, trong cc thanh ghi dng chung d liu ca ngi dng a ch t 20h n 7Fh. Cc

thanh ghi PORTA, PORTB, PORTC, PORTD, PORTE u cha bank0, do truy xut d liu cc thanh ghi ny ta phi chuyn n bank0. Ngoi ra mt vi cc thanh ghi thng dng khc cng cha bank0. - Bank1 gm cc nh c a ch t 80h n FFh. Cc thanh ghi dng chung c a ch t A0h n EFh. Cc thanh ghi TRISA, TRISB, TRISC, TRISD, TRISE cng c cha bank1. - Tng t ta c th suy ra cc nhn xt cho bank2 v bank3 da vo s trn. Cng quan st s trn, ta nhn thy thanh ghi STATUS, FSR c mt trn c 4bank. Mt iu quan trng cn nhc li trong vic truy xut d liu ca PIC16F877A l : phi khai bo ng bank cha thanh ghi . Nu thanh ghi no m 4 bank u ch th khng cn phi chuyn bank. 3.1.5.2.3. Mt vi thanh ghi c chc nng c bit SFR:

Thanh ghi STATUS: thanh ghi ny c mt c 4 bank thanh ghi a ch 03h, 83h, 103h v 183h: cha kt qu thc hin php ton ca khi ALU, trng thi reset v cc bit chn bank cn truy xut trong b nh d liu.

Thanh ghi OPTION_REG: c mt bank2 v bank3 c a ch 81h v 181h. Thanh ghi ny cho php c v ghi, cho php iu khin chc nng pull-up ca cc chn trong PORTB, xc lp cc tham s

v xung tc ng, cnh tc ng ca ngt ngoi vi v b m Timer0

Thanh ghi INTCON: c mt c 4 bank a ch 0Bh, 8Bh, 10Bh, 18Bh. Thanh ghi cho php c v ghi, cha cc bit iu khin v cc bit bo trn Timer0, ngt ngoi vi RB0/INT v ngt khi thay i trng thi ti cc chn ca PORTB.

Thanh ghi PIE1: a ch 8Ch, cha cc bit iu khin chi tit cc ngt ca cc khi chc nng ngoi vi.

Thanh ghi PIR1: a ch 0Ch, chc c ngt ca cc khi chc nng ngoi vi, cch ngt ny c cho php bi cc bit iu khin cha trong thanh ghi PIE1.

Thanh ghi PIE2: a ch 8Dh, cha cc bit iu khin cc ngt ca khi chc nng CCP, SSP b, ngt ca b so snh v ngt ghi vo b nh EEPROM.

Thanh ghi PIR2: a ch 0Dh, cha c ngt ca cc khi chc nng ngoi v, cc ngt ny c ho php bi cc bit iu khin cha trong thanh ghi PIE2.

Thanh ghi PCON: a ch 8Eh, cha cc c hiu cho bit trng thi ch reset ca vi iu khin.

3.1.5.3. Thanh ghi W(work) v tp lnh ca PIC16F877A 3.1.5.3.1. Thanh ghi W: y l thanh ghi rt c bit trong PIC16F877A. N c vai tr tng t nh thanh ghi Accummulator 8051, tuy nhin tm nh hng cua n rng hn nhiu. Tp lnh ca PIC16F877A c tt c 35 lnh th s gp mt ca thanh ghi W l 23 lnh. Hu ht cc lnh ca PIC16F877A u lien quan n thanh ghi W. V d nh: trong PIC chng ta khng c php chuyn trc tip gi tr ca mt thanh ghi khc m phi chuyn thng qua thanh ghi W. Thanh ghi W c 8 bit v khng xut hin trong bt k bank thanh ghi no ca b nh d liu ca PIC16F877A. Mi dng lnh trong PIC16F877A c m t trong 14 bit. Khi ta thc hin mt lnh no , n phi lu a ch ca thanh ghi b tc ng ( chim 8 bit) v gi tr mt hng s k no ( them 8 bit na) l 16 bit, vt qu gii hn 14 bit. Do vy ta khng th no tin hnh mt php tnh ton trc tip no gia 2 thanh ghi vi nhau hoc gia mt thanh ghi vi mt hng s k. Hu ht cc lnh ca PIC16F877A u phi lien quan n thanh ghi W cng v l

do . Khi thc hin mt dng lnh no , th PIC s khng phi tn 8 bit lu a ch ca thanh ghi W trong m lnh ( v c hiu ngm ). C th xem thanh ghi W l thanh ghi trung gian trong qua trnh vit chng trnh cho PIC16F877A. 3.1.5.4. Tp lnh ca PIC16F877A: PIC16F877A c tt c 35 lnh v c trnh by kh r trong datasheet, s dng ngn ng assembly vit, trnh bin dch l MPlab c microchip cung cp min ph. 3.1.5.4.1. Cc vn n v Timer: PIC16F877A c tt c 3 Timer: Timer0 (8 bit), Timer1 (16bit) v Timer2 (8bit). Timer0:

Timer0 ca PIC16F877A cng c 2 chc nng: nh thi v m xung. Hai chc nng trn c th c la chn thng qua bit s 5 TOCS ca thanh ghi OPTION. Ngoi ra, ta cng c th la chn cnh tch cc ca xung clock, cnh tc ng ngt thng qua thanh ghi trn. Timer0 c tch hp trn b tin nh 8 bit (prescaler), c tc dng m rng dung lng ca Timer0. B prescale ny c th c iu chnh bi cc 3 bit PS2:PS0 trong thanh ghi OPTION. N c th c gi tr 1:2, 1:4, 1:8, 1:16, 1:32, 1:64, 1:128, 1:256 ty thuc vo vic thit lp cc gi tr 0,1 cho 3 bit trn. B tin nh c gi tr 1:2 chng hn, c ngha l: bnh thng khng s dng b tin nh ca Timer0 ( ng ngha vi tin nh t l 1:1) th c khi c tc ng ca xung clock th Timer0 s tng them mt n v. Nu s dng b tin nh 1:4 th phi mt 4 xung clock th Timer0 mi tng them mt n v. V hnh chung, gi tr ca Timer0 (8 bit) lc ny khng cn l 255 n m l 255x4=1020. Cc thanh ghi lin quan n Timer0 bao gm: - TMR0: cha gi tr m c TIMER0 - INTCON: cho php ngt hot ng - OPTION_REG: iu khin prescaler Timer1

Timer1 l b nh thi 16bit, gi tr ca Timer1 s c lu trong hai thanh ghi bitTMR1H:TMR1L. C ngt ca Timer1 l bit TMR1IF, bit iu khin ca Timer1 l TRM1IE. Cp thanh ghi ca TMR1 s tng t 0000h n FFFFh ri sau trn v 0000h. Nu ngt c cho php, n s xy ra khi gi tr ca TMR1 trn t FFFFH ri v 0000h, lc ny TMR1IF s bt ln. Timer1 c 3 ch hot ng: - Ch hot ng nh thi ng b: Ch c la chn bi bit TMR1CS. Trong ch ny, xung cp cho Timer1 l Fosc/4, bit T1SYNC khng c tc dng.-

Ch m ng b: trong ch ng b ny, gi tr Timer1 s tng khi c xung cnh lnh vo chn T1OSI/RC1. Xung clock ngoi s c ng b vi xung clock ni, hot ng ng b c thc hin ngay sau b tin nh t l xung(prescale).

- Ch m bt ng b: ch ny xy ra khi bit T1SYNC c set. B nh thi s tip tc m trng sut qu trnh ng ca vi iu khin va c kh nng to mt ngt khi b nh thi trn v lm cho vi iu khin thot khi trng thi ng. Timer2: L b nh thi 8 bit bao gm cc b tin nh (prescale), mt b hu nh Postscaler v mt thanh ghi chu k vit tt l PR2. Vic kt hp Timer2 vi 2 b nh t l cho php n hot ng nh mt b nh thi 16 bit, Module timer2 cung cp thi gian hot ng cho ch iu bin xung PWM nu module CCP c chn.

3.2.

Khi ngun:

3.2.1. S nguyn l:

3.2.2. c im: y l module dng to ra ngun in p chun +5V. S dng IC7805.

u vo l in p xoay chiu sau khi c bin i qua my bin p, a vo b Diode cu cho ra dng in mt chiu (lc ny in p nm trong khong t 7->10V). Sau k hi i qua IC n p 7805 s to ra ngun in p chun +5V cung cp cho mch.

Dng bin p chuyn t ngun 220V AC sang 12V AC cung cp vo module mch ngun ni trn.

Cu diode D1 dng nn dng xoay chiu thnh mt chiu. Khi mch gm cc linh kin R 2,2k , 100k v LED dng bo hiu c ngun cung cp. Cc t trong mch ny u c tc dng lc nhiu ngun vo, cng nh lc nhiu u ra, lm cho ngun tng i n nh, khng b nh hng nhiu bi ti (ti nh). 3.2.3. Linh kin chnh: IC n p 7805:

Vi nhng mch in khng i hi n nh ca in p qu cao, s dng IC n p thng c ngi thit k s dng v mch in kh n gin. Cc loi n p thng c s dng l IC 78xx, vi xx l in p cn n p. V d 7805 n p 5V, 7812 n p 12V. Vic dng cc loi IC n p 78xx tng t nhau.

Ng ra OUT lun n nh 5V d in p t ngun cung cp thay i. Mch ny dng bo v nhng mch in ch hot ng in p 5V (cc loi IC thng hot ng in p ny). Nu ngun in c s c t ngt: in p tng cao th mch in vn hot ng n

nh nh c IC7805 vn gi c in p ng ra OUT 5V khng i. Mch trn ly ngun mt chiu t mt my bin p vi in p t 7V n 9V a vo ng IN. Khi kt ni mch in, do nhiu nguyn nhn, ngi dng d nhm ln cc tnh ca ngun cung cp khi u ni vo mch, trong trng hp ny rt d nh hng n cc linh kin trn board mch. V l do , mt diode c lp thm vo mch diode m bo cc tnh ca ngun cung cp cho mch theo mt chiu duy nht, v ngi dng cng khng cn quan tm n cc tnh ca ngun khi ni vo ng IN na.