Chng 1 Gii Thiu Dng Vi iu Khin STM32

1. Gii thiu dng vi iu khin STM32Nhng c im ni tri ca dng ARM Cortex thu ht cc nh sn xut IC, hn 240 dng vi iu khin da vo nhn Cortex c gii thiu. Khng nm ngoi xu hng , hng sn xut chip ST Microelectronic nhanh chng a ra dng STM32. STM32 l vi iu khin da trn nn tng li ARM Cortex-M3 th h mi do hng ARM thit k. Li ARM Cortex-M3 l s ci tin t li ARM7 truyn thng tng mang li thnh cng vang di cho cng ty ARM.1.1 Mt vi c im ni bt ca STM32ST a ra th trng 4 dng vi iu khin da trn ARM7 v ARM9, nhng STM32 l mt bc tin quan trng trn ng cong chi ph v hiu sut (price/performance), gi ch gn 1 Euro vi s lng ln, STM32 l s thch thc tht s vi cc vi iu khin 8 v 16-bit truyn thng. STM32 u tin gm 14 bin th khc nhau, c phn thnh hai dng: dng Performance c tn s hot ng ca CPU ln ti 72Mhz v dng Access c tn s hot ng ln ti 36Mhz. Cc bin th STM32 trong hai nhm ny tng thch hon ton v cch b tr chn (pin) v phn mm, ng thi kch thc b nh FLASH ROM c th ln ti 512K v 64K SRAM.

Hnh 1. Kin trc ca STM32 nhnh Performance v Access

Nhnh Performance hot ng vi xung nhp ln n 72Mhz v c y cc ngoi vi, nhnh Access hot ng vi xung nhp ti a 36Mhz v c t ngoi vi hn so vi nhnh Performance.a. S tinh viThot nhn th cc ngoi vi ca STM32 cng ging nh nhng vi iu khin khc, nh hai b chuyn i ADC, timer, I2C, SPI, CAN, USB v RTC. Tuy nhin mi ngoi vi trn u c rt nhiu c im th v. V d nh b ADC 12-bit c tch hp mt cm bin nhit t ng hiu chnh khi nhit thay i v h tr nhiu ch chuyn i. Mi b nh thi c 4 khi capture compare (dng bt s kin vi tnh nng input capture v to dng sng ng ra vi output compare), mi khi nh thi c th lin kt vi cc khi nh thi khc to ra mt mng cc nh thi tinh vi hn. Mt b nh thi cao cp chuyn h tr iu khin ng c, vi 6 u ra PWM vi dead time (khong thi gian c chn vo gia hai u tn hiu xut PWM b nhau trong iu khin mch cu H) lp trnh c v mt ng break input (khi pht hin iu kin dng khn cp) s buc tn hiu PWM sang mt trng thi an ton c ci sn. Ngoi vi ni tip SPI c mt khi kim tng (CRC) bng phn cng cho 8 v 16 word h tr tch cc cho giao tip th nh SD hoc MMC.STM32 c h tr thm ti a 12 knh DMA (Direct Memory Access). Mi knh c th c dng truyn d liu n cc thanh ghi ngoi vi hoc t cc thanh ghi ngoi vi i vi kch thc t (word) d liu truyn i c th l 8/16 hoc 32-bit. Mi ngoi vi c th c mt b iu khin DMA (DMA controller) i km dng gi hoc i hi d liu nh yu cu. Mt b phn x bus ni (bus arbiter) v ma trn bus (bus matrix) ti thiu ho s tranh chp bus gia truy cp d liu thng qua CPU (CPU data access) v cc knh DMA. iu cho php cc n v DMA hot ng linh hot, d dng v t ng iu khin cc lung d liu bn trong vi iu khin.STM32 l mt vi iu khin tiu th nng lng thp v t hiu sut cao. N c th hot ng in p 2V, chy tn s 72MHz v dng tiu th ch c 36mA vi tt c cc khi bn trong vi iu khin u c hot ng. Kt hp vi cc ch tit kim nng lng ca Cortex, STM32 ch tiu th 2A khi ch Standby. Mt b dao ng ni RC 8MHz cho php chip nhanh chng thot khi ch tit kim nng lng trong khi b dao ng ngoi ang khi ng. Kh nng nhanh i vo v thot khi cc ch tit kim nng lng lm gim nhiu s tiu th nng lng tng th.b. S an tonNgy nay cc ng dng hin i thng phi hot ng trong mi trng khc khe, i hi tnh an ton cao, cng nh i hi sc mnh x l v cng nhiu thit b ngoi vi tinh vi. p ng cc yu cu khc khe , STM32 cung cp mt s tnh nng phn cng h tr cc ng dng mt cch tt nht. Chng bao gm mt b pht hin in p thp, mt h thng bo v xung Clock v hai b Watchdogs. B u tin l mt Watchdog ca s (windowed watchdog). Watchdog ny phi c lm ti trong mt khung thi gian xc nh. Nu nhn n qu sm, hoc qu mun, th Watchdog s kch hot. B th hai l mt Watchdog c lp (independent watchdog), c b dao ng bn ngoi tch bit vi xung nhp h thng chnh. H thng bo v xung nhp c th pht hin li ca b dao ng chnh bn ngoi (thng l thch anh) v t ng chuyn sang dng b dao ng ni RC 8MHz.c. Tnh bo mtMt trong nhng yu cu khc khe khc ca thit k hin i l nhu cu bo mt m chng trnh ngn chn sao chp tri php phn mm. B nh Flash ca STM32 c th c kha chng truy cp c Flash thng qua cng Debug. Khi tnh nng bo v c c kch hot, b nh Flash cng c bo v chng ghi ngn chn m khng tin cy c chn vo bng vector ngt. Hn na bo v ghi c th c cho php trong phn cn li ca b nh Flash. STM32 cng c mt ng h thi gian thc v mt khu vc nh d liu trn SRAM c nui nh ngun pin. Khu vc ny c mt u vo chng gi mo (anti-tamper input), c th kch hot mt s kin ngt khi c s thay i trng thi u vo ny. Ngoi ra mt s kin chng gi mo s t ng xa d liu c lu tr trn SRAM c nui bng ngun pin.d. Pht trin phn mmNu bn s dng mt vi iu khin da trn li ARM, th cc cng c pht trin cho ARM hin c c h tr tp lnh Thumb-2 v dng Cortex. Ngoi ra ST cng cung cp mt th vin iu khin thit b ngoi vi, mt b th vin pht trin USB nh l mt th vin ANSI C v m ngun l tng thch vi cc th vin trc c cng b cho vi iu khin STR7 v STR9. C rt nhiu RTOS m ngun m v thng mi v middleware (TCP/IP, h thng tp tin, v.v.) h tr cho h Cortex. Dng Cortex-M3 cng i km vi mt h thng g li hon ton mi gi l CoreSight. Truy cp vo h thng CoreSight thng qua cng truy cp Debug (Debug Access Port), cng ny h tr kt ni chun JTAG hoc giao din 2 dy (serial wire-2 Pin), cng nh cung cp trnh iu khin chy g li, h thng CoreSight trn STM32 cung cp h thng im truy cp(data watchpoint) v mt cng c theo di (instrumentation trace). Cng c ny c th gi thng tin v ng dng c la chn n cng c g li. iu ny c th cung cp thm cc thng tin g li v cng c th c s dng trong qu trnh th nghim phn mm.e. Dng Performance v Access ca STM32H STM32 c hai nhnh u tin ring bit: dng Performance v dng Access. Dng Performance tp hp y cc thit b ngoi vi v chy vi xung nhp ti a 72MHz. Dng Access c cc thit b ngoi vi t hn v chy ti a 36MHz. Quan trng hn l cch b tr chn (pins layout) v cc kiu ng gi chip (package type) l nh nhau gia dng Access v dng Performance. iu ny cho php cc phin bn khc nhau ca STM32 c hon v m khng cn phi sa i sp sp li footprint (m hnh chn ca chip trong cng c layout bo mch) trn PCB (Printed Circuit Board).Ngoi hai dng Performance v Access u tin, hin nay ST a ra th trng thm hai dng USB Access v Connectivity nh hnh bn di.

Hnh 2. c im ca bn nhnh trong h STM32

Chng 2 Gii thiu b x l ARM Cortex-M3

I. Gii Thiu Chung1. Gii thiuGii php Soc (System-on-chip) da trn b vi x l nhng ARM c ng dng vo rt nhiu th trng khc nhau bao gm cc ng dng doanh nghip, cc h thng t, mng gia nh v cng ngh mng khng dy... Dng vi x l ARM Cortex da trn mt kin trc chun p ng hu ht cc yu cu v hiu nng lm vic trong tt c cc lnh vc trn. Dng ARM Cortex bao gm ba cu hnh khc nhau ca kin trc ARMv7: cu hnh A cho cc ng dng tinh vi, yu cu cao chy trn cc h iu hnh m v phc tp nh Linux, Android; cu hnh R dnh cho cc h thng thi gian thc v cu hnh M c ti u cho cc ng dng vi iu khin, cn tit kim chi ph. B vi x l Cortex-M3 l b vi x l ARM u tin da trn kin trc ARMv7-M v c thit k c bit t c hiu sut cao trong cc ng dng nhng cn tit kim nng lng v chi ph, chng hn nh cc vi iu khin, h thng c t, h thng kim sot cng nghip v h thng mng khng dy. Thm vo l vic lp trnh c n gin ha ng k gip kin trc ARM tr thnh mt la chn tt cho ngay c nhng ng dng n gin nht.2. Hiu sut cao t c hiu sut cao hn, b vi x l c th lm vic nhiu hn hoc lm vic thng minh hn. y tn s hot ng cao hn c th lm tng hiu sut nhng cng i km vi vic tiu th nng lng nhiu hn v vic thit k cng phc tp hn. Ni cch khc, cng thc hin nhng tc v nhng bng cch nng cao hiu qu tnh ton trong khi vn hot ng tn s thp s dn n s n gin ha trong vic thit k v t tn nng lng hn. Trung tm ca b vi x l Cortex-M3 l mt li c cu trc ng ng tin tin 3 tng, da trn kin trc Harvard, kt hp nhiu tnh nng mi mnh m nh suy on vic r nhnh, php nhn c thc thi trong mt chu k v php chia c thc hin bng phn cng to nn mt hiu nng vt tri (im Dhrystone l 1,25 DMIPS/MHz). B vi x l Cortex-M3 h tr kin trc tp lnh Thumb-2, gip n hot ng hiu qu hn 70% cho mi MHz so vi mt b vi x l ARM7TDMI-S thc thi vi tp lnh Thumb, v hiu qu hn 35% so vi b x l ARM7TDMI-S thc thi vi tp lnh ARM.3. D s dng, pht trin ng dng nhanh chng, hiu qu

Tiu ch quan trng trong vic la chn b vi x l l gim thi gian v chi ph pht trin, c bit l kh nng pht trin ng dng phi tht nhanh chng v n gin. B vi x l Cortex-M3 c thit k p ng mc tiu trn. Ngi lp trnh khng cn phi vit bt k m hp ng no (assembler code) hoc cn phi c kin thc su v kin trc to ra mt ng dng n gin. B vi x l c m hnh lp trnh da trn ngn xp c n gin ho tng thch vi kin trc ARM truyn thng nhng tng t vi h thng c trin khai trn kin trc 8 v 16-bit, gip vic chuyn tip n kin trc 32-bit d dng hn. Ngoi ra mt m hnh ngt da trn phn cng s gip vic vit cc chng trnh x l ngt tr nn n gin hn bao gi ht, chng trnh khi ng c th c vit trc tip bng ngn ng C m khng cn bt k mt lnh assembly no so vi kin trc ARM truyn thng. Cc tnh nng chnh mi trong tp lnh Thumb-2 bao gm vic thc hin m lnh C mt cch t nhin hn, thao tc trc tip trn cc bit, php chia phn cng v lnh If/Then. Hn na, nhn t gc pht trin ng dng, Thumb-2 tng tc pht trin, n gin ha vic bo tr, h tr cc i tng bin dch thng qua ti u ha t ng cho c hiu sut v mt m m khng cn quan tm n vic m c bin dch cho ch ARM hoc Thumb. Kt qu l lp trnh vin c th m ngun ca h trong ngn ng C m khng cn to ra cc th vin i tng bin dch sn, c ngha l kh nng ti s dng m ngun ln hn nhiu.4. Gim chi ph pht trin v nng lng tiu th

Chi ph lun l ro cn ln nht cho s la chn mt b vi x l hiu sut cao. B vi x l c thit k trn mt din tch nh s gim chi ph ng k. B vi x l Cortex-M3 thc hin iu ny bng cch ci t cc li ARM nh nht t trc n nay, ch vi 33.000 cng (cng c th l NAND hoc NOR tu vo cng ngh sn xut) trong li trung tm (0.18um G) v bng cch kt hp hiu qu, cht ch cc thnh phn trong h thng vi x l. B nh c ti gin bng cch ci t b nh khng thng hng (unaligned), thao tc bit d dng vi k thut bit banding. Tp lnh Thumb-2 tit kim b nh hn 25% so vi tp lnh ARM. p ng nhu cu ngy cng tng trong vic tit kim nng lng cc ng dng mng khng dy, b vi x l Cortex-M3 h tr m rng xung nhp cho cc cng (c th ngng cung cp xung nhp cho cc cng tit kim nng lng) v tch hp ch ng. Kt qu l b vi x l ch tiu th 4.5mW in nng v chim din tch 0.3 mm2 (silicon footprint) khi trin khai tn s 50MHz trn qu trnh cng ngh TSMC 0.13G, s dng t bo tiu chun ARM Metro.5. Tch hp kh nng d li v theo vt trong lp trnh

H thng nhng thng khng c giao din ngi dng ha (GUI) lm cho vic g li chng trnh tr thnh mt thch thc tht s i cc lp trnh vin. Ban u, b ICE (In-circuit Emulator) c s dng to mt ca s theo di h thng thng qua mt giao din quen thuc nh trn PC. Tuy nhin khi h thng ngy cng nh v phc tp hn, phng php ny khng cn kh thi na. Cng ngh g li ca b vi x l Cortex-M3 c ci t trong chnh phn cng ca n (kt hp vi mt vi thnh phn khc) gip g li nhanh hn vi cc tnh nng trace & profiling, breakpoints, watchpoints v bn v li gip rt ngn thi gian pht trin ng dng. Ngoi ra, b vi x l cn cung cp mt mc nhn cao hn vo h thng thng qua cng JTAG truyn thng hoc cng SWD (Serial Wire Debug) ch s dng 2 ng tn hiu, thch hp cho cc thit b c kiu ng gi nh gn.6. Chuyn t dng x l ARM7 sang Cortex-M3 hot ng v s dng nng lng hiu qu hnTrong gn mt thp k qua, dng vi x l ARM7 c s dng rt rng ri. B vi x l Cortex-M3 c xy dng trn nn tng ny nn vic nng cp t dng ARM7 ln Cortex-M3 l hp l v d dng. Li trung tm lm vic hiu qu hn, m hnh lp trnh n gin, cch x l ngt tt nh (deterministic interrupt behaviour), vic tch hp cc thit b ngoi vi gip nng cao hiu nng lm vic m vn gi c chi ph thp.

Bng 1. So snh ARM7TDMI-S v Cortex-M3 (100MHz - TSMC 0.18G)(*: Khng bao gm cc thit b ngoi vi (MPU & ETM) hoc cc thnh phn tch hp khc)

Hnh 1. So snh hiu sut gia ARM7TDMI-S (ARM) v Cortex-M3 (Thumb-2)

Hnh 2. So snh kch thc m lnh gia ARM7TDMI-S (ARM) v Cortex-M3 (Thumb-2)

II. C Ch To Xung Ca Cortex M31. Kin trc v tnh nng vi x l Cortex-M3B vi x l Cortex-M3 da trn kin trc ARMv7-M c cu trc th bc. N tch hp li x l trung tm, gi l CM3Core, vi cc thit b ngoi vi h thng tin tin to ra cc kh nng nh kim sot ngt, bo v b nh, g li v theo vt h thng.Cc thit b ngoi vi c th c cu hnh mt cch thch hp, cho php b vi x l Cortex-M3 p ng c rt nhiu ng dng v yu cu kht khe ca h thng. Li ca b vi x l Cortex-M3 v cc thnh phn tch hp (hnh 3) c thit k c bit p ng yu cu b nh ti thiu, nng lng tiu th thp v thit k nh gn.1.1 Li Cortex-M3Li trung tm Cortex-M3 da trn kin trc Harvard, c c trng bng s tch bit gia vng nh cha d liu v chng trnh do c cc bus ring truy cp (hnh 3). c tnh ny khc vi dng ARM7 da trn kin trc Von Neumann s dng chung vng nh cha d liu v chng trnh, do dng chung bus cho vic truy xut. V c th c cng lc lnh v d liu t b nh, b vi x l Cortex-M3 c th thc hin nhiu hot ng song song, tng tc thc thi ng dng.

Hnh 3. B vi x l Cortex-M3

Li Cortex c cu trc ng ng gm 3 tng:Instruction Fetch,Instruction DecodevInstruction Execute. Khi gp mt lnh nhnh, tng decode cha mt ch th np lnh suy on c th dn n vic thc thi nhanh hn. B x l np lnh d nh r nhnh trong giai on gii m. Sau , trong giai on thc thi, vic r nhnh c gii quyt v b vi x l s phn tch xem u l lnh thc thi k tip. Nu vic r nhnh khng c chn th lnh tip theo sn sng. Cn nu vic r nhnh c chn th lnh r nhnh cng sn sng ngay lp tc, hn ch thi gian ri ch cn mt chu k.Li Cortex-M3 cha mt b gii m cho tp lnh Thumb truyn thng v Thumb-2 mi, mt ALU tin tin h tr nhn chia phn cng, iu khin logic, v cc giao tip vi cc thnh phn khc ca b x l.B vi x l Cortex-M3 l mt b vi x l 32-bit, vi rng ca ng dn d liu 32 bit, cc di thanh ghi v giao tip b nh. C 13 thanh ghi a dng, hai con tr ngn xp, mt thanh ghi lin kt, mt b m chng trnh v mt s thanh ghi c bit trong c mt thanh ghi trng thi chng trnh.B vi x l Cortex-M3 h tr hai ch hot ng (Thread v Handler) v hai mc truy cp ti nguyn ca li x l (c quyn v khng c quyn), to iu kin cho vic ci t cc h thng m v phc tp nhng vn bo mt. Nhng dng m khng c quyn b gii hn hoc khng cho php truy cp vo mt s ti nguyn quan trng (mt s lnh c bit v cc vng nh nht nh). Ch Thread l ch hot ng tiu biu h tr c m c quyn v khng c quyn. B vi x l s vo ch Handler khi mt ngoi l (exception) xy ra v tt c cc m l c quyn trong ch ny. Ngoi ra, tt c cc hot ng trong b vi x l u thuc mt trong hai trng thi hot ng: Thumb cho ch thc thi bnh thng v Debug cho vic g li.B vi x l Cortex-M3 l mt h thng nh x b nh n gin, qun l vng nh c nh ln ti 4 gigabyte vi cc a ch nh ngha sn, dnh ring cho m lnh (vng m lnh), SRAM (vng nh), b nh/thit b bn ngoi, thit b ngoi vi bn trong v bn ngoi. Ngoi ra cn c mt vng nh c bit dnh ring cho nh cung cp.

Hnh 4. Bn b nh

B vi x l Cortex-M3 cho php truy cp trc tip n tng bit d liu trong cc h thng n gin bng cch thc thi mt k thut c gi l bit-banding (hnh 5). B nh bao gm hai vng bit-band (mi vng 1MB) trong SRAM v vng b danh 32MB ca vng khng gian ngoi vi (Mi byte trong vng b danh s tng ng vi mt bit trong vng bit-band). Mi hot ng np/lu ti mt a ch trong khu vc b danh (alias region) s trc tip tng ng vi hot ng trn bit c i din bi b danh . C th, khi ghi gi tr 0x01 vo mt a ch trn vng b danh th c ngha l xc nh bit tng ng s c gi tr l 1, tng t gi tr 0x00 s xc nh bit tng ng c gi tr 0. Cn c gi tr ti mt a ch vng b danh c ngha l c c gi tr ca bit tng ng. Mt vn cn ch na l hot ng ny mang tnh nguyn t (khng chia nh c na), khng th b gin on bi cc hot ng khc trn bus.

Hnh 5

Cc h thng c da trn ARM7 ch h tr truy xut d liu thng hng, ch cho php lu tr v truy xut d liu ca mt khi b nh m mi phn t c n v l mt word. B vi x l Cortex-M3 h tr truy xut d liu khng thng hng, cho php chuyn d liu khng thng hng trong mt truy xut n. Thc t, vic chuyn d liu khng thng hng c bin thnh vic chuyn nhiu ln d liu thng hng v c tnh trong sut i vi lp trnh vin (ngha l lp trnh vin hon ton khng cn quan tm n iu ny). Ngoi ra b vi x l Cortex-M3 cng h tr php nhn 32-bit hot ng trong mt chu trnh n v cc php chia c du, khng du vi cc lnh SDIV v UDIV, mt t 2 n 12 chu k ph thuc vo kch thc ca ton hng. Php chia c thc thi nhanh hn nu s chia v s b chia c kch thc tng t nhau. Nhng ci tin trong kh nng ton hc gip Cortex-M3 tr thnh b vi x l l tng cho cc ng dng thin v tnh ton nh c cm bin hoc cc h thng m phng.1.2 Kin trc tp lnh Thumb-2ARMv7-M l cu hnh vi iu khin ca kin trc ARMV7 v khc vi cc kin trc ARM trc ch n ch h tr tp lnh Thumb-2. Tp lnh Thumb-2 l s pha trn gia tp lnh 16 v 32 bit, t c hiu sut ca cc lnh ARM 32 bit, ng thi ph hp vi mt m cng nh tng thch ngc vi tp lnh gc Thumb 16 bit.

Hnh 6

Trong mt h thng da trn b vi x l ARM7, vic chuyn i nhn x l gia ch Thumb (c li v mt m) v ARM (c li v mt hiu sut) l cn thit cho mt s ng dng. Cn b vi x l Cortex-M3 c cc lnh 16 bit v 32 bit tn ti trong cng mt ch , cho php mt m cng nh hiu sut u cao hn m khng cn phi chuyn i phc tp. V tp lnh Thumb-2 l tp bao hm ca tp lnh Thumb 16 bit nn b vi x l Cortex-M3 c th thc thi cc on m trc y vit cho Thumb 16 bit. Do c ci t tp lnh Thumb-2 nn b vi x l Cortex-M3 c kh nng tng thch vi cc thnh vin khc ca dng ARM Cortex.Tp lnh Thumb-2 c cc lnh c bit gip lp trnh vin d dng vit m cho nhiu ng dng khc nhau. Cc lnh BFI v BFC l cc lnh thao tc trn bit, rt c ch trong cc ng dng x l gi tin mng. Cc lnh SBFX v UBFX gip vic chn vo hoc trch xut mt s bit trong thanh ghi c nhanh chng. Lnh RBIT o bit trong mt WORD, c ch trong cc thut ton DSP nh DFT. Cc lnh bng r nhnh TBB v TBH to s cn bng gia mt m v hiu sut. Tp lnh Thumb-2 cng gii thiu cu trc If-Then mi c th xc nh iu kin thc hin ti a bn lnh tip theo.1.3 B iu khin vector ngt lng nhau (NVIC)NVIC (Nested Vectored Interrupt Controller) l thnh phn tch hp ca b vi x l Cortex-M3 c kh nng x l ngt rt linh hot v nhanh chng. Trong ci t chun, n cung cp mt NMI (Non-Maskable Interrupt) v 32 ngt vt l a dng vi 8 mc u tin pre-emption. N c th c cu hnh t 1 n 240 ngt vt l vi ti a 256 mc u tin.B vi x l Cortex-M3 s dng mt bng vector c th ti nh v c, dng cha a ch ca hm x l ngt. Khi nhn mt ngt, b x l s ly a ch t bng vector thng qua bus chng trnh. Bng vector ngt c t a ch 0 khi reset, nhng c th c di chyn n v tr khc bng cch lp trnh mt thanh ghi iu khin. gim bt s cng v tng tnh linh hot h thng, b vi x l Cortex-M3 chuyn t m hnh ngoi l thanh ghi theo di ca b vi x l ARM7 sang m hnh ngoi l da trn stack. Khi c mt ngoi l xut hin th b m chng trnh (Program Counter), thanh ghi trng thi chng trnh (Program Status Register), thanh ghi lin kt (Link Register) v cc thanh ghi a dng t R0-R3, R12 b y vo ngn xp. Trong khi bus d liu y cc thanh ghi ln vng ngn xp th bus chng trnh xc nh cc vector ngoi l t bng vector v np lnh u tin ca m chng trnh x l ngoi l. Sau khi hon tt vic lu tr d liu trn ngn xp v np lnh, chng trnh phc v ngt v x l li c thc thi, tip theo cc thanh ghi s c phc hi t ng chng trnh b ngt tip tc thc hin bnh thng. V thc hin cc hot ng ngn xp bng phn cng nn ta khng cn vit cc on hp ng thc hin cc thao tc trn ngn xp cho cc hm x l ngt truyn thng da trn ngn ng C, gip vic pht trin ng dng d dng hn rt nhiu.NVIC h tr ngt lng nhau, cho php mt ngt c x l trc mt ngt khc da trn mc u tin. N cng h tr cu hnh mc u tin ng cho cc ngt. u tin c th c thay i bng phn mm trong thi gian chy (run time). Cc ngt ang c x l u b kha cho n khi hm x l ngt hon thnh, do , u tin ca ngt c th thay i m khng cn lo n chuyn trng lp.Trong trng hp cc ngt ni ui nhau, cc h thng c s lp li hai ln vic lu trng thi hon thnh v khi phc, dn n tr cao. B vi x l Cortex-M3 n gin ha vic chuyn i gia cc ngt ang hot ng v ang ch bng cch ci t cng ngh tail-chaining trong phn cng NVIC. Tail-chaining t tr thp hn nhiu bng cch thay th chui cc thao tc pop v push vn mt hn 30 chu k xung nhp bng mt thao tc np lnh n gin ch mt 6 chu k. Trng thi b vi x l c t ng lu khi ngt bt u c x l v phc hi ngay khi kt thc, t chu k hn so vi vic thc thi bng phn mm, nng cao hiu sut ng k h thng hot ng di 100MHz.

Hnh 7. Tail chaining trong NVIC

NVIC cng ci t cch thc qun l nng lng ca b vi x l Cortex-M3 tch hp ch ng. Ch Sleep Now c gi bng mt trong hai lnh WFI (Wait For Interrupt) hoc WFE (Wait For Event) s ngay lp tc t nhn b vi x l vo trng thi nng lng thp v ch mt ngoi l (exception). Ch Sleep On Exit t h thng vo ch nng lng thp ngay khi n thot khi hm x l ngt c u tin thp nht. Nhn b vi x l vn trng thi ng cho n khi gp mt ngoi l. V ch c th thot khi ch ny bng ngt nn trng thi h thng khng c phc hi. Bit SLEEPDEEP ca thanh ghi iu khin h thng nu c thit lp c th c s dng kho cng (clock gate) li b vi x l v cc thnh phn h thng khc tit kim in nng.NVIC cng tch hp mt b m SysTick 24-bit m ngc (count-down timer) c th c s dng nh thi to ra ngt, cung cp nhp p mt h iu hnh thi gian thc hot ng hoc cc tc v c lp lch.1.4 n v bo v b nh (MPU)MPU l mt thnh phn ty chn ca b vi x l Cortex-M3, c th nng cao tin cy ca h thng nhng bng cch bo v cc d liu quan trng c h iu hnh s dng khi cc ng dng khc, tch bit c lp cc tc v ang thc thi bng cch khng cho php truy cp vo d liu ca nhau, v hiu ho quyn truy cp vo mt s vng nh, cho php cc vng nh c nh ngha l ch c (read only) v pht hin cc truy cp b nh c th ph v h thng.MPU cho php mt ng dng c chia nh thnh cc tin trnh. Mi tin trnh s c b nh (code, d liu, ngn xp, heap) v thit b ring, cng nh c quyn truy cp vo b nh v cc thit b c chia s. MPU cng c cc quy tc (rule) truy cp ca ngi dng v c quyn bao gm vic thc thi m ti mc c quyn thch hp cng nh quyn s hu b nh v cc thit b ca m c quyn v m ngi dng.MPU chia b nh thnh cc vng ring bit v thc hin vic bo v bng cch ngn cc truy cp tri php. MPU c th chia b nh thnh ti a 8 vng trong mi vng c th c chia thnh 8 vng con. Kch thc vng c th bt u t 32 byte v tng gp i dn cho n ti a 4 gigabyte. Cc vng c nh s th t bt u t 0. C th xc nh mt bn b nh (memory map) nn mc nh truy cp c quyn. Vic truy cp n cc a ch b nh khng c xc nh trong vng MPU hoc khng c php s to ra ngoi l li v qun l b nh (Memory Management Fault Exception).Quy tc bo v vng nh c da trn vo loi tc v (c, vit hoc thc thi) v c quyn ca m thc hin vic truy cp. Mi vng bao gm mt b bit quy nh loi truy cp c php v hnh ng no c php trn bus. MPU cng h tr cc vng chng ln nhau (overlapping regions), tc l c s giao nhau cng mt vng a ch. V kch thc mi vng l bi s ca 2 nn nu 2 vng chng ln nhau th s c th c mt vng nm hon ton trong vng kia. Do , hon ton c kh nng xy ra trng hp nhiu vng nm trn trong mt vng hoc trng hp chng lng nhau. Trong trng hp a ch tra cu nm trong vng chng nhau th kt qu tr v s l vng c s th t cao nht.1.5 G li (Debug) v theo vt (Trace)Vic g li h thng da trn b vi x l Cortex-M3 c thc hin thng qua DAP (Debug Access Port), c th l mt cng SWD (Serial Wire Debug) s dng 2 ng tn hiu hoc mt cng SWJ-D (Serial Wire JTAG Debug) s dng giao thc JTAG hoc SW. Cc SWJ-DP mc nh ch JTAG khi reset v c th chuyn giao thc vi mt chui iu khin c th c cung cp bi phn cng g li bn ngoi.Hnh ng debug c th c kch hot bi cc s kin khc nhau nh breakpoints, watchpoints, iu kin li hoc yu cu debug t bn ngoi. Khi mt s kin debug xy ra, b vi x l Cortex-M3 c th vo ch tm dng (halt mode) hoc ch theo di debug. Trong ch tm dng, b vi x l ngng thc thi hon ton cc chng trnh. Ch ny h tr chy tng bc. Lc ny, mt ngt pht sinh c th b tr hon p ng, c th c thc thi tng bc, hoc b che (masked) nn ngt bn ngoi c th b b qua trong qu trnh debug. Trong ch theo di debug, mt hm x l ngoi l c thc thi thc hin vic g li trong khi vn cho php cc exception c u tin cao hn din ra. Ch ny cng h tr chy tng bc.B FPB (Patch Flash and Breakpoint ) c 6 breakpoint trong chng trnh v 2 breakpoint np d liu, hoc chuyn lnh/d liu t b nh m n b nh h thng. B FPB ny c su comparator so snh cc lnh c ly t b nh m. Mi comparator c th c kch hot nh v li m chng trnh n mt vng trong b nh h thng, hoc thc hin mt breakpoint phn cng bng cch tr v mt lnh breakpoint cho b vi x l. N cng c hai comparator vi nhim v tng t cho d liu.B DWT (Data Watchpoint and Trace) c bn comparator c th c cu hnh thnh watchpoint phn cng. Khi c s dng trong cu hnh ny, comparator c th c lp trnh so snh a ch truy cp d liu hoc b m chng trnh. Cc DWT comparator cng c th c cu hnh kch hot cc s kin ly mu PC, s kin ly mu a ch d liu v lm cho ETM (Embedded Trace Macrocell) pht ra cc gi kch hot trong dng lnh ang c truy vt.ETM l mt thnh phn ty chn h tr vic theo vt lnh m bo rng c th ti cu trc li vic thc hin chng trnh m ch nh hng mt cch ti thiu n b nh. ETM cho php truy vt theo thi gian thc v vic thc thi lnh v truyn d liu bng cch nn thng tin truy vt t nhn b x l gim thiu yu cu bng thng.

Hnh 8. H thng theo vt Cortex-M3

B vi x l Cortex-M3 thc hin vic theo vt d liu bng DWT v ITM (Trace Instrumentation Macrocell). DWT cung cp s liu thng k v vic thc hin lnh v c th to ra s kin watchpoint gi debug hoc ETM trn cc s kin h thng. ITM l cng c truy vt ng dng h tr cch g li kiu "printf" cho h iu hnh v theo vt cc s kin ng dng. N chp nhn cc gi truy vt phn cng t DWT v phn mm theo di s kch thch t li b vi x l v pht ra thng tin chn on h thng nh k. B TPIU (Trace Port Interface Unit) chp nhn cc thng tin truy vt t ETM v ITM, sau ha trn chng, nh dng li v pht ra thng qua SWV (Serial Wire Viewer) n cc b phn tch truy vt bn ngoi. SWV cho php to ra profile cho cc s kin h thng mt cch n gin v hiu qu bng cch xut dng d liu thng qua mt pin duy nht. M ha Manchester v UART l cc nh dng c h tr cho SWV.2.6 Ma trn bus v cc giao din lin ktMa trn bus ca b vi x l Cortex-M3 kt ni b x l v giao din debug n cc bus bn ngoi, ICode, DCode v giao din h thng da trn AMBA AHB-Lite 32 bit, v bus cho cc ngoi vi (Private Peripheral Bus) da trn AMBA APB 32 bit. Ma trn bus cng m nhim vic truy cp d liu khng thng hng v cc vng bit-banding. Giao din ICode 32 bit ly cc lnh t vng nh chng trnh v ch c th truy cp bi CM3Core. Tt c cc ln np lnh u c rng l mt t (WORD), vi s lng lnh c ly trn mi t ty thuc vo loi m thc hin v v tr ca n trong b nh. Giao din DCode 32 bit truy cp d liu t vng nh m chng trnh v c th c truy cp bi CM3Core v DAP. Giao din h thng 32 bit ly cc lnh v truy cp d liu trong vng b nh h thng v ging nh bus DCode, c th c truy cp bi CM3Core v DAP. PPB cho php truy cp vo cc thnh phn bn ngoi ca h thng Cortex-M3.