SAA7283GP データシートの表示（PDF） - Philips Electronics
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SAA7283GP Datasheet PDF : 36 Pages
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Philips Semiconductors
Terrestrial Digital Sound Decoder (TDSD3)
Preliminary specification
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).
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.
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).
1996 Oct 24
10
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