Kutheni izixhobo zeNethiwekhi ziSebenzisa i-25MHz kunye nokuphindaphindwa kwayo njengeeFrekhwensi?

Kutheni izixhobo zeNethiwekhi ziSebenzisa i-25MHz kunye nokuphindaphindwa kwayo njengeeFrekhwensi?

Kwizixhobo zenethiwekhi ezifana namakhadi womnatha, iiswitshi, iirotha, kunye nezixhobo ze-Ethernet, ukhetho lwe-crystal oscillator frequency luchongwa yimisebenzi ephambili yesixhobo, iimfuno ze-chip, kunye nemigangatho yeprotocol yonxibelelwano. Ukusetyenziswa kwe-crystal oscillators kunye nobuninzi be-25MHz kunye nokuphindaphinda kwayo kubangelwa ubukhulu becala ukulungelelaniswa kwenkqubo ye-frequency kunye nemigangatho ye-Ethernet, iiprothokholi zonxibelelwano, kunye ne-architecture ye-chip, eyenza uyilo olulula, ukunciphisa iindleko, kunye nokusebenza okuphuculweyo. Inkcazo ebanzi inikwe ngezantsi:

I. Kutheni Khetha i-25MHz njengeSiseko seFrekhwensi?

25MHz ayiloxabiso elikhethiweyo. Isetyenziswa ngokubanzi ngenxa yokuba inobudlelwane obupheleleyo kunye neefrikhwensi ezininzi ezingundoqo kunxibelelwano lwenethiwekhi, iququzelela ukuphindaphinda okanye ukwahlulahlula.

1.1 Idibana neeMfuno eziQhelekileyo ze-Ethernet

I-Ethernet ekhawulezayo (100BASE- TX): Isebenzisa ikloko ye-25MHz njengesiqhelo sothumelo lwedatha.

Gigabit Ethernet (1000BASE-T): Isebenzisa iwotshi ye-125MHz, eyi-25MHz × 5.

I-10GbE (i-10 Gigabit Ethernet) nangaphezulu: Nangona i-frequency yewotshi ephambili iphezulu (umzekelo, i-156.25MHz), ngokuqhelekileyo inokufumaneka ngokuphindaphinda i-crystal oscillator ye-25MHz nge-PLL.

Oku kubonisa ukuba i-25MHz, njenge-frequency yewotshi esisiseko, inokuxhasa ngokuthe ngqo okanye ngokungathanga ngqo ii-frequencies zokusebenza ze-PHY/MAC zezantya ze-Ethernet eziqhelekileyo.

II. Ubuchule bokuPhunyezwa koBuchule

2.1 Ukuphindaphinda okuLula kokuphindaphinda nge-PLL

Iitshiphu zenethiwekhi (ezifana ne-PHY, i-MAC, kunye neetshiphusi zokutshintsha) zihlala zisebenzisa iisekethe ze-PLL (Isigaba esitshixiweyo) ngaphakathi ukuvelisa amaza ewotshi efunekayo{0}}MHz yingeniso ephakathi enokuthi ivelise ngokufanelekileyo isantya esiphezulu{1}isantya esiphezulu, esinje:

25MHz × 2=50MHz

25MHz × 4=100MHz

25MHz × 5=125MHz

25MHz × 6.25=156.25MHz (ye-10GbE)

Ukusukela ukuba i-25MHz isisiseko esifumaneka lula-u{2}}ukubala inani elipheleleyo lokuphindaphinda, yenza uyilo lwe-PLL lube lula, ivumela ukutshixa ngokukhawuleza, kwaye iqinisekise iziphumo ezizinzileyo.

2.2 Iyahambelana neeMfuno zeChip eziPhambili

Uninzi lwabavelisi be-chip yesixhobo sothungelwano (ezifana ne-Broadcom, i-Realtek, i-Marvell, i-Intel, njl.) ixhasa ngokucacileyo igalelo le-crystal oscillator ye-25MHz kwiimfuno zewotshi ye-PHY okanye i-MAC yazo, okanye unikeze iindlela zokusebenza ze-25MHz igalelo.

III. Izinto eziluncedo kwi-EMC, uYilo lweSekethe, kunye neendleko

3.1 Ulawulo olungcono lwe-EMI kunye neMfezeko yoMqondiso oPhezulu

Xa kuthelekiswa neekristali oscillator ezinezakhelo eziphezulu (umz., 50MHz, 100MHz, 125MHz, 150MHz, kunye ne-200MHz), i-25MHz ibonelela ngezibonelelo ezibalulekileyo ngokwemiqathango yoMbane we-Electromagnetic (EMI):

I-frequency esezantsi esisiseko ibangela uphazamiseko oluncinci lwe-harmonic;

Indlela ye-PCB kulula ukuthobela iinkcukacha zoyilo lwe-EMI;

Iimfuno ezisezantsi zokuvalelwa kunye nokuthembeka kwamandla, ukuququzelela ukuhlanganiswa kwenkqubo.

4

I-25MHz crystal oscillators ziphakathi kwezona zihlandlo zisetyenziswa kakhulu kwishishini le-elektroniki, ngezi nzuzo zilandelayo:

Ininzi kwi{0}}imveliso{1} yeshelufu kunye neendidi ezininzi ezahlukeneyo;

Iindleko eziphantsi zemveliso kunye namaxabiso afikelelekayo okuthenga;

Ikhonkco lokubonelela elikhulileyo elinamaxesha amafutshane okukhokela kunye nomgangatho ozinzile.

Oku kunomtsalane kakhulu kubavelisi besixhobo sothungelwano ababandakanyeka kwimveliso-enkulu.

IV. Umzekelo weSicelo kuYilo oluSebenzayo

Ukuthatha iGigabit Ethernet switch njengomzekelo:

I-chip ephambili yokulawula idinga igalelo lokusebenza rhoqo kwe-125MHz;

Kuyilo, i-crystal oscillator ye-25MHz ingasetyenziswa, kwaye i-frequency inokuphindaphindwa ukuya kwi-125MHz nge-chip eyakhelweyo{2}}kwi-PLL;

Okwangoku, iwotshi ye-25MHz inokuhanjiswa kwezinye iimodyuli (ezifana ne-PHY, i-MAC, okanye iimodyuli zongqamaniso lwewotshi) ngomthi wewotshi;

Oku kuphumeza umthombo wewotshi edibeneyo, yenza lula ulwakhiwo lwewotshi, kwaye kunciphisa ubunzima benkqubo kunye neendleko.

Isishwankathelo

Izizathu zokuba kutheni izixhobo zenethiwekhi zisebenzisa i-25MHz kunye nokuphindaphindwa kwayo njenge-crystal oscillator frequency inokushwankathelwa ngolu hlobo lulandelayo:

I-Hangjing Crystal Oscillators isetyenziswa ngokubanzi kwizixhobo zenethiwekhi (amakhadi enethiwekhi, iiswitshi, ii-routers, i-Ethernet). Ukongeza kwimveliso-yemigangatho yemveliso, sikwabonelela ngokubanzi-ubushushu obuphezulu{3}}iioscillator ezizinzo zekristale (-55~{5}} isidanga) kwaye sinokubonelela ngesicelo secrystal oscillator kunye nezisombululo ezihambelanayo. Ukuba unezidingo ezifanelekileyo, nceda uzive ukhululekile ukuqhagamshelana neentengiso ze-Hangjing okanye abasebenzi bobugcisa.