EF9345 datasheet(20/38 Pages) STMICROELECTRONICS

20 / 38 page

Random access to a variable code is obviously not

as easy. The EXP, KRE and CMP commands are

designed to facilitate this task (figure 17).

The EXP command translates a full row of variable

codes into a row of expanded codes. Expanded

codes are generally not displayable by very similar

to the long codes.

KRE gives a random access to an expanded code

and makes it appear as a regular long code.

The CMP command translates a full row of ex-

panded code into a row of variabble codes and

minimizes the file size in the process.

These commands use a buffer pair as working

area.

Fixed Short Codes

These fixed 16 bits codes achieve memory saving

by another way. They may be easier to handlethan

variable codes. The penalty is in lesser display

capabilities :

- Accentuated character sets are no longer avail-

able : accentuated characters must be individu-

ally provided by the character generators.

- G’11 and quadrichrome sets cannot be reached.

- Some attributes are latched and can be changed

only while displaying a space (delimitor code).

The KRG command allows an easy access from/to

an 80-byte row buffer in memory to/from the micro-

processor (Figure 19). Figure 20 gives the fixed

short to fixed long translation process which occurs

for each row - while loading the internal row buffer

before display.

BF, XF

D, Y

B, X

KRV COMMAND

Overflow

buffer

D district

number

B (even)

XF :

file pointer

B+ 2

039

B+ 1 = BF

Figure 18 : Variable Codes in memory

D, Y

B, X

KRG COMMAND

District

B (even)

B+ 1

039

Figure 19 : Fixed Short Codes in Memory 80

EF9345

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