Vt100 , apories !!!!!

[Alexios Chouchoulas]

On Thu, 5 Jun 1997, Tasos Sotiropoulos wrote:

> Null modem harakthrizetai to kalwdio pou enwnei katey8eian tis seiriakes 
> portes apo 2 PC. An exeis vt100 terminal, to mono pou xreiazesai einai 
> ena seiriako kalwdio (san ayta pou einai gia ta apla modems...)
> 
> (gia to ypoloipo den eimai poly sigouros, mporei kapoios na me dior8wsei ?)
> seiriakh PC -> DCE (data control equipment)
> seiriakh vt100, modem -> DTE (data terminal equipment)

  Exm, me mperdepses, opote kathisa na to koitaksw. As me diorthwsei kapoios
an lew ahdies pali... Nomizw oti h seiriakh sto PC einai DTE kai oxi DCE.
Pame arga kai apo thn arxh. Yparxoun dyo eidh serial ports (ki as mhn to
kserei o polys kosmos):

  DCE (Data Control Equipment), me arseniko bysma. Afth einai h akrh tou
kentrikou ypologisth (mhn ksexname oti to RS232 ksekinhse gia na syndeei
mainframes kai termatika).

  DTE (Data Terminal Equipment), me thnluko bysma. Afto einai to bysma pou
exei panw tou to termatiko.

  Giati to PC einai DTE? Dyo thewries. (a) exei thlnluko bysma gia tis
seiriakes tou, opws epiballei to EIA standard. (b) h IBM, otan eftiakse to
IBM 5150 (PC), eixe kanonika mainframes sthn paragwgh. Afta tha eixan DCE
serial ports. To PC htan se megethos termatikou kai sigoura den tha
eksyphretouse dika tou termatika sto prosexes mellon. To teleftaio einai
eikasia, alla akougetai logiko.

  H empeirikh apodeiksh einai oti, an to PC eixe DCE bysma, tha arkouse ena
kalwdio me syndesh ena pros ena gia na milhsoume se modems (pou einai DTE --
h mhpws oxi??? Argk, mperdefthka pali). To gegonos einai oti ws twra, ola ta
kalwdia pou exw ftiaksei gia modem eixan xiasti ta TxD/RxD kai CTS/RTS (kai
alla shmata, analoga me to kalwdio kai th xrhsh tou).

  H defterh empeirikh apodeiksh einai oti exw edw to manual enos Cambridge
Z88 (to thymatai kaneis afto; Einai to forhto tou Clive Sinclair -- oso eixe
akoma thn Sinclair Research to onomaze Enigma). Gia thn seiriakh porta tou
Z88 (pou einai thhluko bysma), leei "The Z88 serial port is wired as Data
Terminal Equipment", me to TxD sto pin 2, opws akribws kai to PC. Kai to
kalwdio pou syndeei PC kai Z88 exei xiasti ola ta shmata pou prepei.

  Ara katalhgw oti kai ta PC einai "termatika" symfwna me th seiriakh tous
porta.

  Epeidh ws ena shmeio eikazw (panta me mperdeve h seiriakh s'afto to
shmeio kai ta manuals mou einai sthn Ellada), an kapoios kserei sigoura as
apanthsei.


Alexios Chouchoulas          '88    ,88'   ,88'     alexios at vennea.demon.co.uk
The Unpronounceable One     ,o88oooo88ooooo88oo,              axc at dcs.ed.ac.uk

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