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MP&MC R09 III/IV-ECE
UNIT – VCOMMUNICATION INTERFACE
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JNTUH
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INDEX
• About Serial communication
• Serial Communication Standards
• RS 232
• USART (8251)
• !!! "88
•2#mA Current $oo%
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About Serial cou!icatio!
• Trans&errin' o& ata oer lon' distances usin' %arallel communication is cost e&&ectie and it is not %ossible &or slo*er deices+
• n serial communication one bit is trans&erred at atime oer a sin'le c,annel+
• Serial communication is classi&ied in to
• 1+ Sim%le-
• 2+ u%le-
• 3+ Hal& u%le-3
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About Serial cou!icatio! "Co!t#$
T*o Transmission .ormats1+As/nc,ronous
2+S/nc,ronous
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About Serial cou!icatio! (Contd)
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RS %%
It i' t(e o't coo!l) u'e#
RS *%%
It i' a (i+( ',ee# #i+ital i!terace
RS *%
It ca! be u'e# or +reater #i'ta!ce'.
RS **9
U'e# or ,oi!t to ,oi!t or ulti#ro, "o!e 'e!#er u, to 0reci,ie!t'$ cou!icatio!'.
RS *12
It ca! (a!#le (i+( ',ee#' a!# lo!+ cable #i'ta!ce' u, to *000 eet.
Serial Communication Standards
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RS 232
RS232 (Recommended standard232) is a standard inter&acea%%roed b/ t,e !lectronic ndustries Association (!A) &orconnectin' serial deices+
RS232 is t,e inter&ace t,at /our com%uter uses to tal to ande-c,an'e data *it, /our modem and ot,er serial deices+ T,e serial
%orts on most com%uters use a subset o& t,e RS232C standard+
!A introduced RS232 in 1402
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RS 232 (Contd) $ine riers6 Receiers
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RS 232 (Contd) $imitations
• ue to t,e sin'le 7N connection t,e C! andT! must lie in same %lace+
• As t,e aud rate and line len't, increases6 T ,ee&&ect o& ca%acitance bet*een t,e cables causesnoise+
1#
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USART "1%2$ 3loc4 5ia+ra
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USART "1%2$ PIN 5ia+ra
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1%2 i' ,ro+rae# b) u'i!+ t(ree co!trol
re+i'ter'.Mo#e Re+i'ter%.Statu' Re+i'ter
.Coa!# Re+i'ter
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Asynchronous Mode 8251
Tra!'i''io!9
• :,en data c,aracter is sent b/ C;U to 8251 6it adds
start bits6 o%tional %arit/ and sto% bits usin'
As/nc,ronous mode control re'ister &ormat+
• T,is se<uence is t,en transmitted usin' T= out%ut
%in on t,e &allin' ed'e o& T=C+
• Transmission re<uires 1 or 2 sto% bits
• T= out%ut remains ,i', until it detects brea+
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Asynchronous Mode 8251 (Contd)
Reception:
• In Asynchronous mode the CLK frequency
(RXC and TXC i/p) is equa to ! or !" or "#times the $aud rate%
• &aud rate' o% of data $its transmitted/receiedper sec%
• The $it counter ocates start * parity and stop$its%
• Receier requires ony one stop $it%1"
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Asynchronous Mode 8251 (Contd)
• Reception:Reception:
• If +arity ,rror occurs* +arity ,rror -a. is set%
• If a o ee is detected as the stop $it *-ramin. ,rror -a. is set
• If the preious character in the receier $ufferhas not $een read $y the C+0* that data isoerride $y the ne1t data and 2er Run -a. isset%
• A these fa.s are ocated in 3tatus Re.ister of
456!15
USART "1%2$ A ( M #
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USART "1%2$ A')!c(ro!ou' Mo#eI!'tructio! Forat"Mo#e Re+i'ter$
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USART "1%2$ S ( M # I t ti
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USART "1%2$ S)!c(ro!ou' Mo#e I!'tructio!Forat"Mo#e Re+i'ter$
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3tatus Re.ister -ormat for 03ART
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IEEE *11
• I,,,7#44 is a short7ran.e di.itacommunications $us specification%
•I,,,7#44 is an 47$it 5# pin $us%
• The $us empoys si1teen si.na ines
• ,i.ht used for $i7directiona data transfer
• Three for handsha8e
• -ie for $us mana.ement
• ,i.ht .round return ines% 14
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IEEE *11 Co!!ector
T,is standard *as &irst establis,ed in 148US $N!ST,e !!!"88 bus is a multidro% inter&ace in *,ic, all connecteddeices ,ae access to t,e bus lines+ T,e 2" bus lines 'rou% into&our cate'ories9 ata $ines !i',t lines (>1 t,rou', >8) used to trans&erin&ormation (data and commands) bet*een deices on t,e bus6 one
b/te at a time+
Hands,ae $ines T,ree lines used to ,ands,ae t,e trans&er o&in&ormation across t,e data lines9
A?9 ata ?alid NAC9 Not ata Acce%ted NR.9 Not Read/ &or ata 2#
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us @ana'ement $ines .ie lines used &or 'eneral controland coordination o& bus actiities9 ATN9 Attention .C9 nter&ace Clear R!N9 Remote !nable SR9 Serice Re<uest !>9 !nd or denti&/ 7round $ines !i',t lines used &or s,ieldin' and si'nal
returns9 >ne S,ield >ne 7eneral Si'nal 7round Si- lo'ic 'round lines %aired o&& *it, ATN6 SR6 .C6
NAC6 NR. and A?
IEEE *11 Co!!ector "c!t#6$
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IEEE *11 Advantaes
3impe hardare interface
,ase of connectin. mutipe deice to a sin.e
host Aos mi1in. of so and fast deices
9e7esta$ished and mature* idey supported
Ru..ed connectors* hed in pace $y scres*means ca$es cant easiy $e accidentayremoed as they can ith -ire ire and 03&
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IEEE *11 Disadvantaes
;echanicay $u8y connectors and ca$es
Limited speed and e1pansion
Lac8 of command protoco standards
o mandatory .aanic isoation $eteen $us anddeices
<i.h cost (compared to R3 5=5/03&/
-ire ire/,thernet)
Limited aaia$iity (a.ain compared to R3 5=5 /03&/
-ireire/,thernet) 23
%0 A C 7
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%0A Curre!t 7oo,
.or di'ital serial communications6 a current loo% is acommunication inter&ace t,at uses current instead o& olta'e&or si'nalin'+
Current loo%s can be used oer moderatel/ lon' distances(tens o& ilometres)+
$on' be&ore t,e RS232 standard6 current loo%s *ere used tosend di'ital data in serial &orm &or tele%rinters+
>lder telet/%es used a 0# mA current loo%+ $ater mac,ineso%erated on a lo*er 2# mA current leel+
@ost earl/ minicom%uters &eatured a 2# mA current loo%inter&ace6 *it, an RS232 %ort 'enerall/ aailable as a more
e-%ensie o%tion+2"
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!u""#dup"e$ 2% &A Curre!t 7oo, Circuit
Anot,er *a/ &or leaa'e current control is inserts
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'i&p"e$ 2% &A Curre!t 7oo, Circuit
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AN* +,-
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