Sharp mz-800 Instrukcja Obsługi Pobierz pdf (Strona 14)

I

MZ-800

4-2-5. Scroll

1)

Scrolling is possible

for

both

horizontal

and

vertical

directions

by

means

of

software

offset.

The

following

four

registers are

use~

for

scroll

control.

a.

Scroll start address register: SSA (7-bit)

b.

Scroll end address register: SEA (7-bit)

c.

Scroll

width

register:

SW

= SEA-SSA (7-bit)

d. Scroll offset register:

SOF (10-bit)

(

x y z

I

SEA

+--

__

I

I

I

I

!

l,

___

_

)

---

2)

Control

of

scroll starts

by

the

initialization

of

the

scroll control register.

SSA

= $0

SEA = $7D

SW

= $7D

SOF = $0

3)

Way

of

smooth

scrolling

SOF = $0

~

$5

Programming

"SOF =

$5"

makes

the

display

screen

shifted one line up.

The highest line (address:

$0 - $27) is then assigned

to

the

lowest

line

($1

F18

-.:

$1

F3F).

As

normal

scroll

involves

updating

of

the data

for

the

lowest

line,

the

data

of

address

$1

F18

-

$1

F3F

are

updated.

SOF = $5

~

$0

By reducing the value

of

SOF

by

"5",

it

makes the

screen shifted one line

down.

SEAL-

____________________________

~

13

4)

Line scroll

SOF =

$O~

$28

Programming

"SOF =

$28"

makes

the

display screen

shifted

eight

lines up. Data on the highest line

therefore shifted

to

the

bottom

line.

Programming

"$28

~

$0"

makes the

display

screen

shifted

eight

lines

down,

and

the

line

on

the

bottom

moves

to

the

highest

line.

5)

Screen

split

Appropriate

deviation

of

SSA. SEA, and

SW

permits

to

divide

the

screen

into

three sections

of

®,

® and

©.

Though

the

section ® is

permitted

to

scroll, sections

® and © are

not

permitted

to

scroll.

See the

figure

to

explain

with.

@

SSA-.

®

SEA-.

©

Assume

now

that

the

top

of

the

section ® is on the

5th line

(40 raster) and

the

top

of

the section © is on

the 18th line (144 raster).

Attention

must

be paid to

the fact

that

values SSA and SEA are used

for

assigning lines. Scroll registers are set

with

the

following

values.

SSA

= $19

SEA

=

$5A

SW

=

$41

SOF = $0

In

this

occasion,

it

needs

to

initialize

the

screen that

has been displayed.

"SOF =

$5"

must

be program-

med

to

scroll ® one line. Then,

only

the

section ® is

shifted

up, and

the

highest

line

of

® moves

to

the

bottom

line

of

®.

Programming

"SOF =

$A"

makes

it

scrolled one

more

line.

SOF

~

SW

Scroll offset (SOF)

should

necessarily be

within

a

range

of

the

scroll

width.

Display is

not

assured

with

SOF set greater than SW.

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