SAA7283ZP datasheet(10/36 Pages) PHILIPS

10 / 36 page

1996 Oct 24

Philips Semiconductors

Preliminary speciﬁcation

Terrestrial Digital Sound Decoder (TDSD3)

SAA7283

User mute

The error counter is an 8-bit counter which locks at

count 255. The counter is reset and its output sent to the

I2C-bus every 128 ms. This enables the user to interrogate

the number of errors occurring within a 128 ms period.

The user can then mute the device by pulling pin MUTE

LOW (this function is also provided by the MUTE bit in the

I2C-bus) or setting SILENCE bit LOW in I2C-bus to switch

input of audio switching buffers to analog ground.

Switching buffers

The analog switches select between the output of the

DACs, the FM input and an external input (EXT).

Switching is controlled by bits in the I2C-bus and internal

switching function. The external analog inputs should be

≤1.1 V (RMS) at the input pin, and the output buffers have

a voltage drive of 1 V (RMS).

NICAM/FM audio level matching

Differing audio headroom and alignment levels occur

between systems I and BGH, due to the differing systems

and broadcast standards. In order to match the NICAM

and FM audio output levels without requiring application

changes, the device will automatically switch in 4.6 dB

attenuation network in the NICAM path for system BGH

(this can be disabled by setting the NICLEV bit LOW in

I2C-bus). A programmable attenuation network in the FM

path only, controlled by bits in I2C-bus, provides additional

flexibility for user to match FM and NICAM audio levels

(see Table 9).

Power-on reset state

Two pins control the initial set-up of the device during

power-on reset.

PORA (Power-On Reset Audio)

When pulled LOW the device will be configured with a

12 dB gain in the oversampling filter and the C4OV bit in

the I2C-bus will be set HIGH. This pin when HIGH will

configure the device with a 6 dB gain in the

oversampling filter and will set C4OV bit in the I2C-bus

LOW.

PORM (Power-On Reset Mute)

This pin when LOW will mute the output of the device at

power-on by setting the SILENCE bit in the I2C-bus

LOW. To put the device back into a normal mode of

operation the SILENCE bit in the I2C-bus must be set

HIGH.

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