Dot Matrix Printer Users Manual

DEFINING YOUR OWN NLQ CHARACTERS

As youprobablynoticed,NLQcharactersareprintedby two passesof the

printhead.Halfofthecharacterisprintedonthefirstpass,andtheremainder

onthesecondpass.Thepaperisrolleduphalfadotheightinbetweenpasses

to letthe printheadprintdotson the secondpassthatoverlaptheprevious

dots,in otier to fillin thespacesandproducedensercharacters.Addition-

ally,tie print head speedis halved,andthe dots areprintedat doublethe

densityof draftcharacters.Forthisreason,NLQcharacterscancontainup

to 23 dotsin thehorizontaldirection.

Fundamentally,theprocessto defineandprintdownloadedNLQcharacter

is the sameas for draft charactem,exceptthat youmustsupplyaboutfour

timesasmuchcharacterdata,andyoumustdesignthecharacterwiththe?SVO

passes of the print head in mind. There are small diffextmceswith the

standardmodein the way the attributeinformationis processedalso.

In the draftqualitymodethe attributebytecarriesthedescenderdata,and

specifiesthe leftspaceandthecharacterwidth.In theNLQmode,the first

bit also carries the descenderdata, and the next three bits describethe

character’sleft space as with the draft charactem,but the last four bits

describetherightspace.Appropriateallocationof datain thesesevenbits

lets you place the character whe~ you like within the grid, with the

nxtrictionthatthe charactermustbe at least9 dotswide.

UsethegridinFigure5-4tohelpplotthedata.Duetothetwo-passprocess,

NLQcharacterscancontainupto 16dotsvertically.ml tom23arethedata

forthe firstpass, andm24to m46are thedataforthe secondpass.

To makethecharacterdataeasierto calculate,putthefirstpassdotsinside

theboxesonthegridwhenyouaredesigningyourcharacters,andthesecond

passdotsonthelines.Rememberthatadjacentdotsmaynotoverlaponthe

samepass;inotherwords,ifonedotis inabox,itsadjacentdotonthesame

passmaynotbeonaline.l%erefom,tomakesmoothcharactm, putthedots

neededtooverlapanyspacesin a characterin theappropriateplacesin the

secondpassgrid.

Ifweplotourcar-shapedsymbolforNLQ,thegriddatawilllooklikeFigure

5-5.

Thedefiningprocessisthesameasfordraftcharacters,exceptthatyoumust

selectNLQmode,and you mustdefine46 data.If you wish to printyour

NLQ characterswith the regularcharacterset, the remarksregardingthe