AO-CONTROL (AUTOSTANDARD Control)

Address

: 0E

Type

: R/W

Reset

: 0001 1111

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

MUTE OV

MONO OV

UNMUTE

C4 OV

STANDARD CHECK

AUTOSTANDARD controls the audio matrix when the user has selected the DAC as source (AUD-MX-

CNT bits[6:4] = 010). In this case it will mute the outputs or select MIN. These functions can be overriden

by bits 6 and 7 below.

MUTE OV

: Mute override, 1 = mute (override AUTOSTANDARD)

forces the audio signal to be muted.

MONO OV

: FM/AM Mono override, 1 = mono (override AUTOSTANDARD) forces

can be used to force to analoguesound. This may be useful in the case of marginal NICAM

reception to prevent automatic switching.

AUD-MX-CNT bits[6:4]

bit 7

bit 6

AO1 source

010

0

0

DAC

X

1

MIN (in case of L/L’ standard)

0

1

FM (in case of B/G or I standard)

1

1

Muted (in case of B/G or I standard)

1

0

Muted

UNMUTE

: Nicam Un-mute, 1 = unmute

allows the NICAM decoder to be unmuted if the bit error rate is higher than the preset limit;

this overrides the automatic switching to FM or AM which would normally occur.

C4 OV

: CBI4 override, 1 => CBI[4] forced to 1 internally

is used to override the 4th NICAM control bit (reserve sound switch) if required. This bit is

transmitted by the broadcaster to indicate that the analogue sound carrier is a backup of

the NICAM signal; this is usually the case. If the NICAM signal fails, the STV8203 will

automatically switch to backup sound if the received bit was set to 1. If this bit was set to

0 and bit 4 set to 0, the decoder will stay switched to analogue sound. If bit 4 is set to 1,

the received CBI4 is ignored. Note that if automatic standard is off, switching between

analogue and NICAM audio must be done manually.

STANDARD

CHECK

: Controlthechoiceoftransmissionstandardstobesearchedforbytheautomaticstandardfunction

(standardsearchactive whenbit= 1).The morechoices,thelongerthesearch time. Ifthesystem

in use can be identified by the characteristics of the video signal, for example by the chroma

demodulator,then only a single bit needs to be set. In this case, the AUTOSTANDARD function

willprogram thedemodulatorfor thechosenstandard.If no bits areset,the AUTOSTANDARD

function is disabled andall registers need to be set manually.

bit 3 - Run check for standard 3 (L/L’ - AM/NICAM)

bit 2 - Run Check for Standard 2 (B/G - FM/NICAM)

bit 1 - Run check for standard 1 (B/G - Stereo)

bit 0 - Run check for standard 0 (I - FM/NICAM)

AO-TIMEOUT (AUTOSTANDARD Timer Adjustment)

Address

: 0F

Type

: R/W

Reset

: 1010 0101

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

TIME 2 SETTING

TIME 1 SETTING

Time 1 is used for NICAM and FM mono validation and time 2 for Zweiton. If the standard is not found

within this time limit, the next standard will be tried. Time 1 = decimal [bit 3:0] x 32ms. Time 2 = deci-

mal [bit 7:4] x 128ms. Time 1 default value is 160ms. Time 2 default value is 1280ms.

A time of 0ms should not be programmed.

PROGRAMMING THE DEVICE (continued)

STV8203

20/31