Table below depicts 9-bit words required for various functions.

Subsystem’s Configuration

Data Bits

LSB....MSB

Add. Bits

LSB... .MSB

BRIGHTNESS

Min.

Max.

X00000

X11111

000

CONTRAST

Min.

max.

X00000

X11111

100

COLOUR ON/OF F

Off

On

XXXXX0

XXXXX1

010

INSERTION

Allowed

Not Allow.

XXXXX0

XXXXX1

110

SYNC/ASYNC MODE

Sync.

Async.

XXXX0X

XXXX1X

001

VIDEO INT/EXT

Ext.

Int.

XXXXX0

XXXXX1

101

SATURATION B-Y

Min.

Max.

000000

111111

011

SATURATION R-Y

Min.

Max.

000000

1111

111

A demultiplexer directs the data towards latches

which drive the appropriate control. More detailed

information about serial bus operation is given in

the following chapter.

Video Switch

The video switch has three inputs :

- an internal video input (pin 37),

- an external video input (pin 35),

- a synchro input (pin 39),

and two outputs :

- an internal video output (pin 38),

- a switchable video output (pin 40)

The 1Vpp composite video signal applied to the

internal video input is multiplied by two and then

appears as a 2Vpp low impedance composite

video signal at the output. This signal is used to

deliver a 1Vpp/75

Ω composite video signal to the

peri-TV plug.

The switchable video output can be any of the three

inputs. When the Int/Ext one active bit word is high

(address number 5), the internal video input is

selected. If not, either a regenerated synchro pulse

or the external video signal is directed towards this

output depending on the level of the Sync/Async

one active bit word (address number 4). As this

output is to be connected to the synchro integrated

circuit, RGB information derived from an external

source via the Peri-TV plug can be displayed on the

screen, the synchronization of the TV-set being

then made with an external video signal.

When RGB information is derived from a source

integrated in the TV-set, a teletext decoder for

example, the synchronization can be made either

on the internal video input (in case of synchronous

data) or on the synchro input (in case of asynchro-

nous data).

R, G, B Inputs

There are two sets of R, G, B inputs : one is to be

connected to the peri-TV plug (Ext R, G, B), the

second one to receive the information derived from

the TV-set itself (Int R, G, B).

In order to have a saturation control on a picture

coming from the R, G, B inputs too, it is necessary

to get R-Y, B-Y and Y signals from R, G, B informa-

tion : this is performed on the first matrix that

receives the three 0.9Vp (100% white) R, G, B

signals and delivers the corresponding Y, R-Y, B-Y

signals. These ones are multiplied by 1.4 in order

to make the R-Y and B-Y signals compatible with

the R-Y and B-Y TV mode inputs. The desired R,

G, B inputs are selected by means of 3 switches

controlled by the two fast blanking signal inputs. A

high level on FB external pin selects the external

RGB sources. The th ree selected inputs are

clamped in order to give the required DC level at

the output of this first matrix. The three not selected

inputs are clamped on a fixed DC level.

Y, R-Y, B-Y Inputs

The 2Vpp composite video signal appearing at the

switchable output of the video switch (pin 40) is

driven through the subcarrier trap and the lumi-

nance delay line with a 6 dB attenuation to the Y

input (1Vpp ; pin 12). In order to make this 1Vpp

(synchro to white) Y signal compatible with the

1Vpp (black to white) Y signal delivered by the first

matrix, it is necessary to multiply it by a coefficient

of 1.4.

R, G, B Insertion Pulse (fast blanking)

A R, G, B source has also to provide an insertion

TEA5040

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