Digital Equipment DECwriter Correspondent User manual

I
'DECwriter
,C, oirir!e ,s, pondent
Technical IM, anua 'I
Prepared by !Educational Services
, Of
Digit.a.I Eq ui pment co ,r po ,ration

Copyri ght C 1' 983 . by Digi t al Eguipm ent Corporat i on .
Al l JU.,gbt ,s : Re . serv-ed.
Printed i :n u. .. s •.A ,.
• ffle r~prodl!ctlon of thi s ,m ater ial , i'n , pa · rt o r wh ol ,e, is strict l y
prohib i ted .. For -C · ~PY inf -o r mation, ,c,on ta c t t be Ed uc ationa l Services
De,l)iJranent, · 019 i ta l 'Equi t pn ent Cor
1
po ratf. on ,, Ma y.n ar d ., Massachusetts
,f ,1 754.
Tae i• Dform.atio,n .~n t:t1i s doc , ument . is subj , ect t o c h •. mg e •wi thout
, not i ce ,. Pi -g i ta l Eq1,1 .i, ptnent • Co : rpor:.atlon .a ·s swnes no .r •es po ns i b Hi ty
tot . any err , or ,s · ttu:it may a: p,pear in · th:ts docume nt ..
e aston"" ond Nate-N-Lok..,. . ar •e tr.adeJnar .k·s -of A:M P., Inc .
The fo llo ..w h>g a.r,e tr , pdemar ' ks of Dig i. t.al ·Eg,i..i': pm ent ,c or po rat io n,
Hayn ~r d, Ka'" e;ac tu.1setts.
;-
. 1)1(: '
OECaa te
DECnet
pro ay s te#J, -1, e
D!CS YST EM • 2, U
' DEC11t i · ter
DlBOL
, 01 ca 1" .AL
; LA ·
MA · SS B U.S
POP
P/POS
f . r: ,o'f.e-s,s ion a 1
Ra :i, nb ow
RSTS
nsx
IJ :NlBUS
'V,AK
VHS
VT
Work Pr. oc , es , sor
CHA ! PTER l
Ll
1..2
1.• 2. l
1.2.2
1.2.3
l. 2.4
1.3
1.4
Cf . AM-ZR 2
2.1
2.2
2.3
2.4
2.5
2.5.1
2.5.l. l
.2. s.1.2
2 . 5.• 2
2.5.3
2.5 .•-4
2. 5.• -4 . l
2.5. - 4.2
2. •6
2. , 6.l
2.•1 6. 2
2. ·6 .• 3
2. , 6.4
2. , 6.5
2.7
2.7.1
2.7 . 2
2.7.3
2.8
CONTC:NTS
GE ' NE : RA 'L DESCRIPTION
General
....·• ·• .. ... ..·•.........·• ·• ...........-• ......
Simplified Description•••·••·•·••••·••••••••••··
Character Printing·· · ·••••••••••••••••••••••
Ch , aract - er Se · ts . ... .. . ................... . ....... .
Rib 1b- on C- ar · tr i1 dge •• _ •••• . ••••••• • ••••••••••••••
Physical Description of Components ••••••••••
Related Docuntents ••••••••• . •••••• • •••••••••••••••
Specifications •••••••• • •••••••••••••••••••••••••
OPER1aT-OR INF• ORMATION
,G- eneral ,. ,. ••••••••••••••••• . •••••• • •••• • •• •• ••••••
Ter : minal Con, tr , ols .. .............. . ............. . . .
· visual Indicators . •••••••••••••••• • ••••••••••••••
Audible Indicators ••••••••••••••••••••••••••••••
Keybo . ar ,d K,e; ys •••••••••• .,. ••• . •••••••••••••••••••••
St _ and , ar .d Keys •• . •••••••••• . •••••••••••••••••••
Au,t 1 0 Re: peat • • •••.•••••••••••••••••••••••
CAPS LOC:K Key ........................... .
F: unc - ti ; on Keys ....... .. . ... _ ................ . .. . ... .
Flnbedd , ed Numeric Keypad Keys ................ .
SET-UP - Key •••••••• , ••••••••••• . ••• • •• .• . ••••••••
Entering SET-UP••••••••••••••••••••••·••
Exiting SET-UP ............. . ........... . . .
SET-UP••••••••••••••••••••••••••• • •••••• •• ••••••
s ,t .a·: tus He.s. sa . g.e .............. .. . ... . .... . ........ .
F:o : rm Fea ,t -u:r ; es .. . .......... . .... . .. . ............. .
Communic.atio , ns Features •••••••••••••••••••••
Keyboard Features •••••••••••••••••• • • • ••••••
P'r in ·t: er Fe .a tu.res .... . .......... . .... . ... . .. .. . ,. ••••
Memor·y · Fea ·t u·r, es ... .. .. . ................... . ........... .
Ope . ra · tin .g Me. mory • •••••••••••••••••••••••••••
Us.e: r: Perm.anent He.mory ••••••••••••••• •• •••• • •
Def a:ul t Memor·y ...... .. .. .. . . ................... .
External Keypad Modes •••••••••••••••••••••••••••
iii
1-1
1-2
1-4
1- -4
1-5
1-5
1-6
1-7
2-1
2-1
2-1
2-4
2-4
2-6
2-6
2-6
2-6
2- ·6
2-9
2-9
2-9
2-9
2-9
2-10
2-11
2-20
2-23
2-32
2-32
2-33
2-33
2-36

CR&P'fER 3
:3.•1
), .. 2
3 .. 3
3.3 . l
3.3. '2
3 .. 3. 3
3.• 3 .. 3 .. 1
3.•) .• 3•.2
3. 3. 3. 3
3,. 3.4
3.3.5
· 3. 3 .5 .•l
3.3.S.2
3,. ) ,, . s. 3
3.3.S.-4
3 .. 3.5 .S
3.• 3,. 6
3, .. 3. '7
:3 ,. 3 .. 7.1
3 .:3.7 .•.2
) . 3 .. 7.3
3.• 3.,:8
3. 3, .9
3.3.' !l. 1
· i.3 .. ,9 .. 2
3. .• 3 .. l0
3.3 .• u, ... 1
3. 3 .. 19.2
3. 3 .. 11
3 .. 3 .. lLl
'.}. ,: 3. 11.2
3 .. 3.• 12
3, ,.3 . 12 . l
3,. 3.12 .. 2
3.l.ll
J.• J.U
4.1
4.2
11.2. 1
• • 2. ,2
4.l .. 3
4.2.·4
4. 2 .. ,4 . 1
•. 2 .. A .2
•• , 2.,,4 • .3
A .. 2 .. 5
41 .2~'5.,l
THEORY , OF
1
0PERATION
: Gene :r·,al .. ,. ,. , .•• ,., .. -• ; ...... . .. .. ,,. . ..... .. , .. _ ..... . ... . . .. ,. ..... .. ,. .. .
In ;t :r; od: : uc :t :i- on .• ,., .•.•.• , .. .. . .. ;. ... . . .. .. . ... ,. .•••• • , ••••• -•, ••••• "" •
·p·, uncti : on , al : Overv i-e ,w . ........ .. , _.. .. . ..... .. ,• . •••• , •• ,. •• ~ ••• . ••
: Rec .e i.ved · Cb . ar ,a. cte : rs •.••• .• . ••.••••• -• , ••• • .• -• ..... .. .
Transmitted , Cba . r.acters •.••• .• .• , ......... . .......... .
'Hicro , pr , ocess o· r/COntr , ol System ... . .......... . ... . ..
' Tick J: nterr
1
u pt .... . ..... .. . ....... . .. . ...... . .... .. ..
Receiv - er 1, nterru,pt . .. . .. . ... ,. ,. . ,. . •••••••• .• . ••••
Do"t FlFO 'I. nt.err , upt • . ••••• .• . ••••• .• . •.••••••••
ln:i .- t.iali . zation iR outin ,e .... . ............... . .... .
Communi , c.ati , ons and l/0 Data Process i ng ••••••
Data : Fo:rma .t ., ••• , ••••.•• .• .• , ., ........ ,. ... ...... .. .. .
D.ata Handling Thr oug h the USART •••••••••
Ba
1
ua . : Ra .· te Cl ; oc · k: ·s •• ,. . ....... . ........ ,. ,. ,. ••• ,• •
J, nterface Signals and M odem Control •••••
Comm : un ic . ations : Fi r, mware ••• . ••••••• .• . •••• . ••
·iKe_ yboa :r ,d , .. ,. , .... ,. ,.. , ..... . ... ,. • ,. • .• ,. ,. ,. . .... .. . , •••• . •• .• , ••
' Print i, ng and ' Print ' head Positioning
: pr ; oce : ss ,. .• ,. ,. ,.. •• ,. , .. ,.. •• .• , ....... .. .. ,. ,. _, •••• .• ,. ,. , •••••• • ,.
, o,t e rv i :e w ,. . .. ,. ,. , .... . .. ,. ,. ,. • . •• .• , .. ,. .. • • • • .• • , •• .• .• .• ,• .•
Se · rv - o/ . Kead Posi·t . io : ning ...... .. . .... . ... .... .
Cbarac · ter Printing •••• .• • •..•• ••• .• . •••••• . •••
-Pa:per . Adva : nce !P. rocess ,. ,. .. , ,. ....." .. . .. . .. , ., "' , •• ,. • .• , •• , ••••
! Po,w er . Supply and Distribution •••• .• .• . ••••• . ••••
Power · oi ,s· tr ib , ut i o:n ...... ,. • .• . ••• ,. •••.••••••.
H7 . 83 '9 : Power Sup _ ply •• ,. • .• ••• • ,. . ............... .
: Nonvolatile RAM :(:NVRAH) .• .• . •••••••.•••• .• . •• ••• • .•
N\1 : RAN ·[)e·v_i ;c1 e ,. ,. ,. ,. , .. ,•.•..• ,. . .. _ .,.. , .. , ••• ,. .. . .... . .. , •• . ,. •••
NV , RAN Timing
•••••.......................
30 : 0/129 ,1 Baud J: , otegral M odem ................ .
F, unc:ti · onal Desc:ri:pt i,on . ... .. . ....... . .. .. .... .
Tb- eo· ry ,o:f •()p.e, t.a ·t . ion . .. . .. . ... .. .. . .. . .... .. .. . .... .
: 2e , m-J. Curr,ent Lo. op Adapte r , Option
;00'n,f .i, gu : .r ; at :i; ons ... ,. ,. ,. ,.... ,. , ••• .• ,. ,• • ~ . ... ........ ,. .•
In te ,r f.ace Spe .c i f i c ,a t i ons .......... . . ..... .
;&,rt, er - na .l Ke-y , pad ()p •t ion .• .• • • • •.• • • .. • • • • •• • • • • .. ..
Ac -o. ustlc: Coupl , er :Modem •• . •• ,. . .... ,. • .• . •••• ••. •••••
1'1110UBL&StfOOT . l•G
·Gene:t - al ...... ,• .•, ,. • ,. .• .• .• . •••.• .• .•.• . •• . •• . • .. • ,, . ...... .. . .. . ....... .. ..
'f :e.r,minal
Se l f-Tes ts
6el:f-T,e ,s ,t :He l p : Messa9,e • .• . ••••• . •••• ,. ..... . ..... .. ..
PQw,er•-:Up . Sel : f- • te s· t: ,. • .• ,. •• ,. • . •.•.•• ,. . . ... , ••• . •• . •• ,. . ••
Pr lnter ,S. el ·f- -T,e ,s· ts ,• .•.• . •• .•.• ,. ,. •• .• . •••••• ., •• ••• .• ,.
e1 · 1-, Opera-tio ,o &el · f- ' Test ·s • • .• . •.•.•••• .• . •••• • .• .• •• •
ll .n,a,l. og ' Loo,pbac :k · Te ,G·t .•.• ,. • .• .• . •••• .• •• . •• ,. • • . ••
B,uid RA,t.e and :Li ne Slgnal • f'est ,. ......... .
ful 1 Du ,pl , ex .. ..... , ... ,. ,• .• ,. , •• , ... .. ... "' !. , ... . .. .. , ••• ., .• ,. ,.
, In teg.tal :Mod , eJD {DCM) Test ••••••••••• ,. .. . ..... .
,A•n .~log Loopbac ,k T es ·t •• , •••• .• . •.•• ,. •• • • ,. •• .• .•
3-1
3-1
3-3
3-4
3- :6
3-7
3-10
3-12
3-12
3-14
3-1 ,4
3-14
3-16
3-18
3-20
3-22
3-24
3-27
3-27
3-3 ,0
3-31
3-3.2
3-34
3-34
3-34
3-3,6
3-37
3-39
3-4 ,0
3-4 •0
3-40
3-45
3-4 ,6
3-4:6
3-47
4-l
4- 1
4-2
4-4
4- 5
4- '5
4-5
4-7
4 -8
4-9
4-9
4.2.S.2
4.2.6
4.2.6.l
4.2.7
4.3
4.• 3.1
4.3.2
4. 4
4.4.l
4.4.2
4.4 .• 2, .l
4.4.2.2
4.4.2.3
4.4 .. 2.4
4 .. 4.2.5
4 .. 4. 3
4. - 4.4
4.4.5
4 .• , 4. ·6
CHAPTER '5
' 5.1
5.2
5.3
' 5.4
5 .• 5
5. ,6
5.• 7
5.8
5.9
5.1 -0
5.11
5 .1 2
5.13
5.14
5 .1 5
5 .1 ' 5.l
5.1 · 5. 2
5. 15 .3
5. 1'5. 4
5.• 15.5
5.• 15 . 6
5.•1 5.7
5 . l' S. 8
5.• 16
5.• 17
5.18
5.• 19
APPBIJIDIX A
A:PPEN:0 1X B
Remote Oat.a Loopback Test •••••••••••••••
Acoustic Coupled Modem {ACM) Test •••••••••••
Analog Loopback Test ••••••••••••• • ••••••
20 mA Lo- opb.ack Test •••••••••••••••••••••••••
T~oubleshooting •••••·······••••••••········•• • •·
S. el f- 'T. ests ••••••••••••••••••••••••••••••••••
Tr - oubleshoot i ng T.abl , es ...................... .
Function . al Tes - ts ............................. ... . .
Powe :r S.u_ pply •••• ,. . . .................. .. ...... .
Logic Board ••••••••••••••••••••• • •••••••• •••
Wak- e-Up · Test ..... . ...................... .
System Clocks •••••••••••••••••••••••••••
Interrupts ••••••••••••••••••••••••••••••
: Bell Test •••••••••••••••••••••••••••• . •••
DC Serv - o/Encoder Test •• •••••••••••••••••
Print Character Te.st ••.••• •••• •••••••• •• ••••
Line Fe .e.d Test ....... . ..... . .... .. ............ ..
USART T. est . ................................. .. .
Keyb .o. ard · Test . •••••••••• • •••••••• .• •••••••••••
: MECHANCIAL SERVICING
Gener al •••• .• ; •••••••••• . .•••••..•••••••••• •• ••••••
Pr in · thead .............. . .......................... .
Fuse••••••••••••••••••••···•••••••••••••••••••••
B·o · nnet Ho: us i ng ....... . ........... . ................ .
C, ove ·r Housing ... .... .. . ........... . ................ .
Acoustic .Coupler Assembly . •••••••••••••••••••••••
Powe -r . Su _p, pl y ........... . ................... . ..... ..
Keybo , ar ,d Assembly • •• •••• . ••••••••••••••••••• . •••••
Ke yboard Bezel •••••••••••••••••••••••••• • •••••••
I:n· teg ·r al Mod -em Board ••••••••••••••••••••••••••••
T, elephone Interface Cable Connector Assembly ••••
Extern.al Connecto .r Ass - embly •• •••• •••••••••• • ••••
A,C En , try Assembly . . ..... .... . .. . ................... ..
P- ower ,(1/0) Switch . Assembly and Filter ••••••••••
Printer Mechanism As.sernbly •••••••••••••• ••• •••••
. St . epp . er Motor •••••••• . ••••••••• .•.• ••••••• . •••••
Ser - ,.ro Motor ••• . ••••••••••••••••••••••••••••••
Bail B. ar Assembly .......................... ..
Pl _a, te ,n ,As: sembl y •••••••••••••••••••••••••••••
Carr iag .e Ass , embly ••••••••• •• •• •. •••••••••••••
Upper Ribbon Driv ,e Cable ••••••••••••••••••••
Lower Ribbon Dr i-v ,e Cable ••••••••••••••••••••
, parallel ism Adjusting P.:oc . edure ••••• • •••••••
In-terl - oc ·k Switch As. sembly •••••••••••••••••••••••
Pa
1
p,e· r- j Out s, witc :h •••••• , ••••••••• , ................... .
Lo.g ic Bo . ar ;d ....... . ................... . ........... .
Roll Paper Holder ••••••·······•·••••·• • ••••·•·••
C, 0NTROL CHARACTERS 1.N0 ESCAPE SBQUBNCE SUMMARY
INTERFACE
V
4-10
4-11
4-11
4-12
4-13
4-13
4-13
4-24
4-24
4-26
4-26
4-28
4-28
4-29
4-30
4-32
4-36
4-38
4-40
5-1
5-1
5-4
5-5
5-6
5-7
5-8
5-10
5-11
' 5-12
5-13
5-14
5-15
5- 16
5-17
5-19
5-20
5-21
5-22
5-23
5-25
5-26
5-26
5-28
5-30
5-31
5-32

,FIGURES
1-2
1-3
1-4
2- 1
2-2
3 - 1
3-2
3-3
3-4
3- 5
3-6
"3-7
3 -'8
3 _g
3- 1 0
3- 11
3-12
:3-13
3 -1 .il
3-1'5
~- 1~
J. -J '7
.3-18
3-19
J-2e
3- 21
3- 22
i -23
.3 -2'4
3-25
3- 2~
3-21
~- 1
4 -2
,-3
~-,1
jJ-5
~-6
~- 1
.... ti
◄ -9
-4- 18
"4- 11
A-12
..f -13
,f-1 ◄
4 ... 15
4--1.,6
4 -17
4 - lS
Local ·Mo-de •• _. ... .. .. ,. .. _ •• .• • •• _ ......... . ....... .. .. .. _. _ •• • .•
Line 'Mode ....... .. .... .. .. ,. , ... .. . . ... .. . . . ...... , .,. ... .... .. ,. ••
OECwrit.er co , rrespondent Dia gra m ••• ,. ,• . •••••• .• • ••••
Tei:mi.nal · Co : nt.rols • .• ,. ,. ,. .... , •••• •• . •• ,. .. ... ,. ,. • _ •• _ •• . •.••
Vi csua1 and Co l um :n Indi ,c, a:tors •••••• .• •.• ••• . •• . ••••••
DECwriter Corresponde ,ot .B lock Diagram ........... .
Data Flow for Received Chara cte r . . ..... ...... ..... .
Data :F-1ow for Tr a nsmitted Character ••• ••• •• ~ ••••
Mic:roproces so r/ , Control System · Logic • ••• , •• •• ••• • •
Tick lnterr , upt Flow Dlagr ,am •• ,. ,. ... ...... .. ... .. . .
Rec.eive,r Interrupt Flow Diagram •• •••• • •.• • . ••••• . ••
Dot F If'O Int e rrupt Fl , ow Diagram . . ..... . ......... .
Seria l I>a' ta 'Fo:rmat.:s .• ,. •• _.., •• ,. ... . .. ,. .... . ... , ... ,. ••• .• ••
Data Handling in th e US.A:RT •••• . ••••• .• ••• •••• •• •••
-Ci:eating Baud 'Rate Clcocks .• • ••••• ,. . ••• .• ,• .• .• . •• ••••••
int erface Sig . nal :R e cognition and , Contr , ol • ,. ••••••
:Receive Character Processing Routine . •••••••• ,. •••
Transmit ' Cbacacter P:r, ocessi , ng Routine ••••••••• ••
Ke_yboa.ra .I.o-g ic ••••••• ,. ,. ,. ... .. . .. ,. ...... ,. • •••• . ••• ,. •••
JCeyboard Array Internal Addr , ess itng •••••••••• .• . •• •
Sn . eat Path ,. .. .. ... ................ ,. ,. . . . .. . ... ....... .. __ •• • ..
Printing and P rinthead Pos iti oning Process ••••••
~- I d . • . .
. ~~ vo , Hea • P:>s1t1on . 1ng Log.1c . •• • •• .• . •••••• . •• .••. •• .• .•
Pr:1nt. :1n 9 Log:1c ,,,, -.. - - • -• ... ,. .. , •• • ,. ,. , ••• • ·• , ,. , •• ••• ·• .• ·• ... ·· •.
Paper :Feed 'Sub: sys ,t.em Logic . . ....................... .
DEC-writer Cor.res . pondent Power Distribution •• ••••
fl7839 Power Supp ly Functional Block Diagram •••••
£'Rl4,UJ tlVRAN :B lo c.k Diagram . •• .• , .... .. . ...... .. .. .. ... . .. ..
tlVRAM Timing Di ag.t:ams •• ,..• ,.. ••• •• .• .• .• .• ,. .. . .. . ...... .. .. .
Int egra l Modem f'unctio , nal Bl , ock Diagram • , ... .... . .
lnter.face .St.at.e's ,. .• ,. ,. ,. ,. • ,. ,. ,. ,. ,. ~ •• -• .• •••• ,• .••••••• ,. , ••
Acoustic Coup l er Bl ock Diagr ,am . ............ ,. •• •••
Se lf -Tes-t flelp 'He ,s. sage • .• _ .. .. .. .. .. .. . .. . .. . .. .. . .. .. . .. .. .. . .
Character Pat:tern Prin · tou ·t . .. .. . .......... .. .. ..... ..
Single - Character Prirrtout ......... ,. . . ... .. . . ,. ••. ••• .• . ••
£1 A _ Loopo · ack Connector ,. ,. • ,. • ,. .. .. ,. . .. . .. .. ... ,. .• .• ,. •• .• .•
1 nstal li ng th e ElA Loopback Connector • ,. •• ••• .. •• •
1'_c. oubleshoc ·t i :n9 Fl · o.wcbart • ,. • ,. •• • .• • . ••••• .• , ••••• . •••
D:ECwri ter CO.rz es pondent Pbys ic ,a l /f ': unctional
Block D.i agr.a.Bl , • ,. ,. ,.. ......... .. .·_ ........ ,. •• ,. .. . ... . _ ••• .• . •••
AC Vo1 tages ,. ... _.JI) .• .- ·" . . .... . ,• .• ,. • .• . •• * •• ,. ,. , ••••• , ,. ,. ,. . ..... ..
DC .Wake-Up 'Waveform ... .. ... .. . ..... .. .. . .. . .... ,. •• . •• , •••
· Cloc:k Test Jfavefo.1:i:11 .s ,. .. ,. .. ,. •• •••••••• .• . ••••• .• .• , •••• .•
l nterr upt 'Test Wa ·i ,,.e ,f orm ·s ,. ,.. ....... . .. .. . ,. •. ••••• • ••••
flel l Test W.a v-e·f orm .• C ... . .... _ ,. _ ••• ,. .. ,. •• •• , . . . .... , • • •• • ,. ,. •• • ••
Servo ttotor Encoder Wa11.efor, 111 • •• , ,. ,. ,. ... ,. ••••• • ., .• •• •
DC Servo ~otor Stepped Left to Bi ,ght •••••• • •••• .•
X Servo iiOtor , stepped Bight -to Left ........... . .
1'est Poirfts f , or s,ol enoids .. ~ • .• , ..... . .. , ..... . ... .. .... .
~511ef o, cm of Good DC305 ,. . . ........... , .. . .... . ... . .. . ...... .. .
Wavefo.r:Jfl of Go od D.r:iv.er and T.rans:ist.or .,. ..... . .. .
vi
1-3
1-4
l-5
2-2
2-3
3-2
3-4
j -6
3-8
3-11
3-12
3-13
3-15
3-17
3-1 '8
3-2 1
3-22
3-23
3 -24
3-25
3-27
3-29
3-30
3 -31
3-32
3-34
3-35
3-37
3-39
3-42
3-46
3, -48
4-2
4-.3
4-3
4 -5
4- ,6
• 4-21
4-25
4-26
4-27
4-28
4-28
• 4-29
4- 30
4-31
4-31
4-32
4-33
4-33
4-19
4-20
4-21
4-22
4-23
4-24
4-25
4-2 ,6
4-27
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5- '8
5-9
5-1 ,0
5-11
5-12
' 5-13
5-14
5-1 "5
5-16
5-17
5-18
5-19
5-20
5-21
' 5-22
5-23
5-2 ,4
5-25
5-26
5-27
2-l
2-2
2-3
2-4
2-5
2-6
2-7
2-8
2- 9
2-10
3 -1
3 -2
3 -3
Waveform of Open PN :P Transistor •••••••••••••••••
Waveform of Open 284l Dr i ve 'r ••••••••••••••••••••
Waveform of Shorted PNP Transistor ••••••••••••••
Waveform of Shorted 2841 Driver •••••••••••••••••
Check . of Stepper Motor Windings •••••••••••••••••
Wav , eform , of DC305 ' Line Feed Output ••••••••••••••
Line Feed lnput vs Output (LFl or LF2) ••••••••••
Line Feed Input VS Output {LF3 or LF4) ••••••••••
USART Serial Data , (tower Case m) • •••••••••••••••
FRO Re.moval Sequence •• . •••••••• .• . •••••••••••••••••
Printhead ••••····•••••••••••·••••••••·····••••··
Fuse •••• • •••••••••••••••••••••••••••••••••••••••
Bo:n: ne ·t Hous i ' ng ••••• . ••••••••• .• , ••••••••• . ••••••••••
Co v, er ·Hou·s i ng ••• .• .• . •••• • •••• . •••••••• . •••••••••••••
Acoustic Coupler Housing Assembly •••• •••••••••••
P,o· wer S: uppl 'Y Bo. ar -d •••••• . •••••••••• .• . •••••••••••••
Keyboa · rd Assembly •• . ••••••••••••••••••••••••••• . ••
l(eybo .a·r,d ca · bl , es • .• •••••••••• . •••••••• . •••••••••••••
Keybo,a· rd · Bezel •••••• .• .• . ••••••••• . •••••••••••••••••
I· nteg . ral Modem Board •••••• .• .• . ••••• •• •••••••••••••
Telephone I; nterfac ,e Cable Connector Assembly ••••
External Co· nnector Assembly •••••••••••••••••••••
AC : Entry Assem· bly •••• , .. . ......................... .
Po , wer Sw•. tch ( 1/0) Wiring •••••••••••••••••••••••
Pr i : nter ' Me . cha · ni sm .. .. .... . ........................ .
S·t, eppe ·r Motor •• ••.•• , ••••••••• .• ,. ........ . .......... .
T, ensioning Dev ice and Servo Assembly ••••••••••••
Bail · ea -r . Assembly ................................ .
Platen Ass , embly •••••• . ••••••••••••••••• , ••••••••••
Carriage Assembly •••••••••••••••••••••••••••••••
' Ribbon Drive Cables •••••••••••••••••••••••••••••
Par.al lel ism Adjustment .• . •••••• •• ••••••••••••••••
Interl , ock S· wi t •cb Assembly ••••••••• •• ••••••••••••
Pap . er- . Out , Swi tc :h . .. . .. .. . .... . ......... . ...... .. .. . ...... .
Logic Board Connectors ••• • • .• . •••••••• . •••••• • •••••
Ro l l Paper Hol, der . ....... . ................. .. . ....... .
T,e. rmi . nal Cont :r . ols ... . .............................. .
Vi sual J:nd .i, c. at ; or :s .. . ... .. . . .. .. . ........ . .. . .. . ...... . .... .
Bell Tone Indications ••••••••• . ••••••••••••••••••
F unc tion Keys •••••••••••••••••.•.•••••••...•••••
1
F,o: rm Fea ; tur , es . .. . . ... . .......... . ..... .. .. . ......... ,.
Commu ni cations F. eatur , es •••••••••••••••••••••••••
Keyboard Fe ,a ture :s . •••.••• . ••• •••• • ••• ••• .• . •••••••••
Pr i O't : er Fea t1 ure .s ,. , ••••••••••••••••• ,. . •••••••• .• . •• ••
STORE, RECA ' LL, and RES , ET Fea · tures •••••••••••••••
Feat .o re Default Values ••••••• •••• . ••• •• ••••••• •••
System Addr , ess Map •••••••••••••• ••••••••••••••••
Hardware Interrupt Vectors ••••••• , •••••••••••••••
USART Baud Rates and Clock Frequencies••••••••••
vii
4-35
4-35
4-35
4-35
4-36
4-37
4-37
4-38
4-40
5-2
5-3
5-4
5-5
5-6
5-7
5-9
5-10
5-11
5-11
5-12
5-13
5-14
5-15
5-1 ,6
5-17
5-19
5-20
5-21
5-22
5-24
5-26
5-27
5-29
5-30
5-31
5-32
2-3
2-4
2-5
2-7
2-11
2-12
2-20
2-24
2-34
2-35
..3-9
3-10
3-19

3-4
3 -5
, f- 1
4-2
4- 3
4 - 4
4 - 5
4-6
4- 7
4 -8
4-9
A- 1
B- 1
8- -2
Int e r 'f a ce Signa l States .. .. . ....... . ..... .. ...... . .. . .... .
NVRAM I nput - Data "B us • . ••••• .• . •••• .• .• .• • •• . •• -• . ... ... . .. .
· power- ·· 0p Se1f - -?es ·t i Faul · ts .. . .. .. .. . ..... .. . ........... .. .
Status 'Ne: ss , age and ' Pr inte :r Se l f - Test ' Faul t ·s ..... .
Status '! Nes ·s , ag -e Fa.ol ts . .. .. .. ... .. .. .. . ..... .. . ....... . .... .
S.i.· ng l e-Ch.ar.acte ·r ' Fau l t ·s •• .• . •••• .• . ••.•• . •• . •.•••••••.• . ••
EU\ A nal og Loo , pback Se lf -Test: , Fau lt s .... . ... . .... ..
DCM . Analog Loopback Self-T - est iFa. ul ts ............ . .. .
DCM iR.emote oat ,a : Lo opb ack Se lf - • Test Faults ..... ~-.
. Acoostic -Cou:pl, ed Modem Se lf -' Test Faul ts • ••••••••
DC · vo l: ta : ge ,S;u, p;pl :y , ... .. ,. ,• . ••• . •• .• • •• .• .• , ... , ••• .• .• ,. , ••••• .• ,.
Pr i nted :Oont : ro l · Cnaracters ...... .. ....... . ........ . .... .
E'l A Inter:face ' Pin . Assignments •••• .• •• ••• . ••.•••••••
2-0 . mA Connecto · r: Pin . Assignm , ents .• • •••• ••• •••• • . •••
viii
3-2 ·0
3-38
4-14
· 4-16
4-2 ·0
4-21
4-22
4-22
4-23
4-23
4-25
A-2
B-1
B-'5

INTRODUCTION
This manual provides maintenance information for the DECwriter
Correspondent. There are four different models of the
COrrespo : ndent. Thes ,e models are described in Paragraph 1.1.
The manual has been prepared for Field Service engineers and other
technical personnel directly involved with maintaining the
DECwr i t, er Correspondent.
Be ,c. ause this manual conce . ntrates primarily on equipment
maintenanc , e, information pertaining to programming and operation
is summarized. For d, etailed discussions of these topics, refer to
the correct docunent .• . (Refer to the list of available doc1ne . nts on
the DECwriter Corr , espondent i .n Paragraph 1.3.}
The manua l is divided into the following chapters.
Chapter l
Chapt . er 2
Chapter 3
General Description -- Provides an overview of the
terminal, an introd , uction to its physical and
functional characteristics, a list of avail able
d, ocunenta t io ·n for the DECwr i ter Correspondent series ,
and specifications.
Controls and Indicators Provid , es a summary of all
the operator controls and indicators on the ter : minal.
Also included is a summary of the SET-UP parameters.
Theory of Operation -- Provides information on the
terminal• s internal operating principles. The chapter
is divided int •o sec ; tlons on the primary functional
areas , of the termi:nal, such as . microprocesb:>r/control
system, I/0 communi:cations . system, keyboard, printing
process, paper advance process, power supply,
nonvol.atil.e RAM, and integral direct connect modem.
ix

, Chapt er 4 Tr ,ou bl e shooting -- Describes t he term i· na l se l f - tests,
provi de s t ro ub l es h oot i ng tab l es, and covers other
hmct i onal t es t s :use ·d to i so l ate fau l 1 ts.
Cbapt , er 5 tsech , ani c .a l .S e 'r vi c in ,g - - Pro v ides the rem , oval and
r e p1 a cem en t proced ur es for al 1 field repl ac , eable
unit s ( FRU s} ..
A:p ; pendi, : A Esca' pe Se , quence Su mm ar y -- 'Pro v id,es a summary of the
· progr a :m mi, ng e s ca : pe seq mm c e s that the D1 ECwr i te ·r
Co·:t: responde :nt , us , es ,.
-ppendix B ln 't e r :fa ce -- Pro vid , es a summar y , of ' the
1
El ,A i , nterface
pin , as s ig nm,e nt s ,.

1.1 GENERAL
CHAPTER 1
GENERAL DESCRIPTION
This chapter describes the DECwr iter Correspondent, . the four
models available, and spe~ifications.
The DECwr iter Correspondent is a microprocessor-control led¥
desktop portable dot matrix terminal designed for use as an
input/output hardcopy machine in computer systems.
The Correspondent hcmdi.es 1200 baud normal text without fill
characters. The maximum print rate is 150 characters per second.
There are four Correspondent models.
Model A
Model B
Model C
Model D
Keyboard send rec , eive (KSR} termin.itl with a
300/1200 baud integral direct connect modem, a
300 baud integral acoustic coupler, and a 50
to 9680 baud EIA port
KSR terminal with a 300/1200 baud integral
direct connect modem and a 50 to 9600 baud EIA
port
KSR terminal with a 300 baud acoustic coupler
and a 50 to 9600 baud EIA port
KSR terminal with a 50 to 9600 baud EIA port
1-1

'
Al 1 models have the same microcode,
operator and host computer features.
available with the Correspondent.
so they support the same
The following options are
Option
LAX12-AL
LAX12-HL
LAX12-JL
LAX12-SP
LAX12-RL
Description
Trac , tor assembly
20 mA current loop interface
APL keycap set
International keycap set
External numeric keypad
Fan fold paper catcher
Large roll paper holder
1.2 SIMPLIFIED DESCRIPTION
Figure 1-1 shows the relationship of the Correspondent to the host
computer . The terminal operates as both an input and outp . ut device
for the computer. When the terminal operates as an input device,
an ASCII character is sent to the computer each time you press a
key on the terminal keyboard. If the terminal is set up for local
echo printing, the character corresponding to the key is printed
at · the same time. As an output device, the termina! receives
printing information from the computer, interprets the
information, and then prints it.
Figure 1-2 shows a simpl ifi~d bl , ock diagram of the correspondent
in local mode. When you press a key in local mode, the keyboard
gene . ra · tes .a code that is sent to the logic board. If the character
is a control character, it is sent to special processing logic. If
the character is a motion characte ,r (such as tab, form feed,
backspace, line feed, or carriage return) or a printable
character, it is sent to the printer mechanics via the
microprocessor control bus on the logic board. The terminal then
prints the character if it i ,s a printable character, or performs
the specified motion such as a carriage return or form feed.
Figure 1-3 shows a simplified block diagram of the Correspondent
in on-line mode. Characters received from the computer are sent to
the logic board via the communication logic. If the character is a
con · trol character, it is sent to special processing logic. If it
is a printable or mo· tion character, it is sent to the pr inter
mechanics via the internal microprocessor control bus. The
terminal then prints the character if it is a printable character,
or performs the motion if it is a motion character.
If · the Correspondent is set · up for local echo, the terminal prints
keybo , ard characters and sends them to the computer. If the
computer has host local echo, it returns these keyb , oard characters
-to the Correspondent.
1-2
llOST CO~PUTER
HOST COMPUTER
Figure 1-1
• ·,.#:
SERIAL DATA OUTPUT
TO HOST
SERIAl OATA ECHO ED
FROM HOST Uf SYSTEM HAS
tiQST ffATURE INC:LUOEOI
. ...,. •... .. . " .
1•1 W11EN USED ASAN INPUT DEVICE
acn A NULL MODEM CABlE
SERIAL DATA SENT
FROM HOST
lb) WHEN USED ASANOUTPUT DEVICE
.... oeo,.,
Computer -- Correspondent Interface
~~~~----------------,
ICORRfSPONOENT
I
I
I
COMM
LOGIC
KEYBOARD
LO<.IC
BOARD
YES
PRtNf OR
MOTION
/110 CHARACTER
CTRL CHARACTER
PROClSStNG
I.OGtr
PRINTER
fJECHANICS
f'RINT
CHARACfER
OR PERFOR~1
MOTIO"I
FU N CTION
L----- __________ .___. -.-.1
Figure 1-2
r'OR ENLARGf:D I\IU
PLEASE SEE FOLLOWING
Local Mode
y . .... ! .. ,
1-3

•
HOSTCOMPUTER
HOSTCOMPUTER
Figure 1-1
(al
SERIAL DATA OUTPUT
TO HOS; ·
8C22·A NULL MOD.EM CABLE
SERIAL DATA ECHOED
FROM HOST Hf SYSTEM HAS
HOST FEATURE fNCLUOEOI
WHEN USED AS AN INPUTDEVICE
BC22 -A NULL MODEMCABLE
SERIAL DATA SENT
FROM HOST
(bl WHEN USED AS AN OUTPUT DEVICE
Computer -- Correspondent Interface
1-3