FUNCTIONAL DESCRIPTION (continued)

The last fourth registers described below are only

available with the STV9421 :

PULSE WIDTH MODULATOR 1

3FF8

V17

V16

V15

V14

V13

V12

V11

V10

*

0

0

00000

0

V1[7:0] : Digital value of the 1

converter (Pin1).

PULSE WIDTH MODULATOR 2

3FF9

V27

V26

V25

V24

V23

V22

V21

V20

*

0

0

00000

0

V2[7:0] : Digital value of the 2

PULSE WIDTH MODULATOR 3

3FFA

V37

V36

V35

V34

V33

V32

V31

V30

*

0

0

00000

0

V3[7:0] : Digital value of the 3

(Pin20).

PULSE WIDTH MODULATOR 4

3FFB

V47

V46

V45

V44

V43

V42

V41

V40

*

0

0

00000

0

V4[7:0] : Digital value of the 4

(Pin10).

Note : * is power on reset value.

II - Descriptors

SPACING

MSB

0

-----

--

LSB

SL7

SL6

SL5

SL4

SL3

SL2

SL1

SL0

SL[7:0] : The number of the scan lines of the

spacing strip (1 to 255).

CHARACTER

MSB

1

DE

-

ZY

-

-

C9

C8

LSB

C7

C6

C5

C4

C3

C2

C1

0

C[9:0] : The address of the first character code of

the strip (even).

DE

: Display enable :

- DE = 0, R = G = B = 0 and FBLK = FBK

(display control register) on whole strip,

- DE = 1, display of the characters.

ZY

: Zoom, ZY = 1 all the scan lines are

repeated once.

III - Code Format

MSB

SET

CHARACTER NUMBER

LSB

BK3 BK2 BK1 BK0

FL

RF

GF

BF

FL : Flashing attribute (the flashing mode is

defined in the DISPLAY CONTROL register).

SET

: The set CHARACTER NUMBER

- If SET = 0 : ROM character,

-If SET = 1 :

• If CHARACTER NUMBER is 0 to

25, a user redefinable character

(UDC) located in RAM at the

addr es s

equal

t o

:

3 8

x

CHARACTER NUMBER,

• If CHARACTER NUMBER is 26 to

63, space character,

• If CHARACTER NUMBER >63,

end of line.

RF, GF, BF : Foreground color.

BK[3:0]

: Background :

- If BK3 = 0, BK[2:0] = background

color R, G and B,

- If BK3 = 1, shadowing :

• BK2 : vertival shadowing,

• BK1 : horizontal shadowing.

(if BK2 = BK1 = 0, the background is

transparent).

IV - Clock and Timing

The whole timing is derived from the XTALIN and

the SYNCHRO (horizontal and vertival) input fre-

quencies. The XTALIN input frequency can be an

external clock or a crystal signal thanks to

XTALIN/XTALOUT pins. The value of this fre-

quency can be chosen between 8 and 15MHz, it is

available on the CKOUT pin and is used by the PLL

to generate a pixel clock locked on the horizontal

synchro input signal.

IV.1 - Horizontal Timing

The number of pixel periods is given by the LINE

DURATION register and is equal to :

[LD[5:0] + 1 ] x 12

(LD[5:0] : value of the LINE DURATION register).

This value allows to choose the horizontal size of

the characters.

The horizontal left margin is given by the HORI-

ZONTAL DELAY register and is equal to :

(DD[7:0] : value of the DISPLAY DELAY register

This value allows to choose the horizontal position

of the characters on the screen. The value of

DD[7:0] must be equal or greater than 4 (the mini-

character periods). The length of the active area,

where R, G, B are different from 0, depends on the

number of characters of the strips.

STV9420 - STV9421

8/16