DEC VT220 - Page 107

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characters

(ROM

space

data)

.

(CRM0-CRM3l)

packed

one

character

per

each

5

data

rows

not

taken

up

by

character

font

data

is

filled

with

FFH

Figure

6-19

shows

that

each

of

the

256

characters

packed

one

character

per

data

row

consist

of

10

bytes

of

data,

one

byte

for

each

scan

line

of

the

character.

When

addressing

one

of

these

characters,

a

single

base

address

is

provided

to

the

character

ROM

by

character

latch

2,

and

each

of

the

10

scan

lines

is

addressed

by

the

address

mux

input.

However,

addressing

the

remaining

32

characters

(CRM0-CRM31)

requires

a

separate

base

address

input

from

character

latch

2

for

every

two

scan

lines

of

the

character

to

be

processed.

Figure

6-20

shows

that

each

of

the

32

characters

packed

into

five

different

data

rows

consist

of

10

bytes

of

data,

one

byte

for

each

scan

line,

but

only

two

bytes

per

data

row.

Later

in

this

chapter,

Table

6-2

describes

the

signals

shown

in

Figure

6-17.

SCAN

LINE

ADDRESS

C

PPLEMENTAL

ARACTERS

PACE

EV.

QUESTION

RROR

HARACTERI

SCII

HARACTERS

M

HARACTERS

27-160)

EC

ECIAL

RAPHICS

HARACTERS

96-126)

.

BASE

I

su

ISL2 ISL3 I

SL41

SLS!

SL6l

SL7 I

SLsl

SL91

SL10

ADDRESS

I

X~O

X=l

X=2

X=3 X=4 X=5

X=5

X=7

X=B

X=9

100X

H/OOOX

Hi

(CRM

32!

f-s

101 X H/OO; x H

f--

(SGC

961

-

;

02X

H

i

002X

H,

103X

H/003X

H

~

(SGC

971

-

(SGC

98)

-

D

104X

Hi004X

H

f--

(SGC

99)

SP

-

G

l;DX

H/O;DX

HE

C

- (

(SGC 124)

-

11

EX

H/O;

EX

H F

(SGC 125)

-

l1FX

H/01FX

H

(SGC

126)

R

120X

H/020X

H (

(CRM

261

~(E

121 X

H/02;

X H

(CRM

331

};

122X

H/022x

H

I--

(CRM

34)

-

123X

H!023X

H

I--

(CRM

351

-

f-

-

17DX

H/07DX

H

I--

-

I-

(CRM

1251

-

17EX

H/07EX

H

(CRM

1251

1 7FX

H/07FX

H

(CRM

127)

lS0X

H/OBOX H

f-

(CRM

1281

-

1

81

X

H/081

X H

I--

(CRM

129)

-

I--

-

CR

C

19EX

H/09EX

H

I--

(CRM

1581

-

11

19FX

H/09FX

H

I--

(CRM

1591

-

1

AOX

H/OAOX H

I--

(CRM

150)

-

1A1X

H/OA

1X H

(CRM

151)

I--

-

1

A2X

H/OA2X

H

(CRM

162)

1

A3X

HiOA3X

H

I-

(CRM

153)

-

J"

I--

-

-=

SU

1F8X HiOFBX H

F="

I-

(CRM

251)

-

CH

1

FCX

H/oFCX

H

I--

(CRM

252)

-

1FOX HiOFDX H

(CRM

253)

1

FEX

H/OFEX H

1

FFX

HiOFFX H

Figure

6-19

Character

ROM

Map:

CRM32-255 and

Special

Graphics

6-23

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