SAA7284GP Philips Semiconductors, SAA7284GP Datasheet - Page 10

• Manufacturer Part Number: SAA7284GP
• Description: Terrestrial digital sound decoder for conventional intercarrier PLL-IF systems
• Manufacturer: Philips Semiconductors

Philips Semiconductors
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
I
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
I
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 I
switching function. The external analog inputs should be
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
I
path only, controlled by bits in I
flexibility for user to match FM and NICAM audio levels
(see Table 9).
1996 Oct 24
2
2
2
1.1 V (RMS) at the input pin, and the output buffers have
C-bus every 128 ms. This enables the user to interrogate
C-bus) or setting SILENCE bit LOW in I
C-bus). A programmable attenuation network in the FM
Terrestrial digital sound decoder for
conventional intercarrier PLL-IF systems
2
C-bus, provides additional
2
C-bus and internal
2
C-bus to switch
10
Power-on reset state
Two pins control the initial set-up of the device during
power-on reset.
PORA (Power-On Reset Audio)
PORM (Power-On Reset Mute)
When pulled LOW the device will be configured with a
12 dB gain in the oversampling filter and the C4OV bit in
the I
configure the device with a 6 dB gain in the
oversampling filter and will set C4OV bit in the I
LOW.
This pin when LOW will mute the output of the device at
power-on by setting the SILENCE bit in the I
LOW. To put the device back into a normal mode of
operation the SILENCE bit in the I
HIGH.
2
C-bus will be set HIGH. This pin when HIGH will
Preliminary specification
2
C-bus must be set
SAA7284
2
C-bus
2
C-bus