EF9345 datasheet(23/38 Pages) STMICROELECTRONICS

23 / 38 page

The cells of one given character set should be layed

in one block.

Up to 100 character cells may be addressed in

each set (or 200 for low resolution quadrichrome

only). The location in memory, where to fetch the

sets in use, are declared by DOR register (Fig-

ure 22). For each type of set, it gives the MSB(s)

of the Z block address. EF9345 reads the Z LSB(s)

in the B byte of the (equivalent) long code. As usual,

the character code is read in the C byte. NT is

derived from the TV line rank in the row and the

double height status.

Loading User Defined Character Set

Before loading a character set into RAM, the user

must :

- Assign a name to the set :

• G’0,G’10 or G’11 for bichrome characters.

• From Q0 to Q7 for quadrichrome charac-

ters.

- Assign a character number to each character

belonging to this set, character numbers range

from 0 to 3 and 32 to 127.

• It is binary coded into 7 bits C(0:6) - C(0:6)

will be loaded later on into a C byte charac-

ter code in order to display the character.

- A pointer to a character slice in memory is then

manufactured from :

• The character number C(0:6)

• The slice number NT(0:3)

• The block number assigned to the set

Z(0:3)

Figure 23 shows how to proceed with the auxiliary

pointer and the OCT command.

Note : The main pointer may be also used. When

sequentially accessing slices of a given

character, auto incrementation is helpless.

6543

210

DOR G’

DOR register

6543

210

XXX

CHARACTER LONG

CODE B BYTE

DOR G’

0 (alpha UDS)

DOR G’

(semi-grap hic UDS)

DOR Q

(quadrichr ome)

Even block

Odd block

1 Kbyte

2 Kbytes

8 Kbytes

UDS Set

Z Address

B7B6B5

DOR

G’

Q0 - Q7

DOR

MEMORY

G’

DOR Q

DOR

Figure 22 : UDS Fetch to Display

EF9345

23/38

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