TDA8745 datasheet(18/40 Pages) PHILIPS

18 / 40 page

1996 Mar 11

Philips Semiconductors

Preliminary speciﬁcation

Satellite sound receiver with I2C-bus control

TDA8745

Table 19 Bits DEM1 and DEM0; De-emphasis; note 1;

see Fig.5

Notes

1. Different de-emphasis characteristics can be selected,

to adjust for different main channel audio carriers.

2. In most cases the de-emphasis needed for main

channel carriers is 50

µs.

3. The NR is to be used with the 75

µs setting for

standard secondary channels.

Table 20 Bit BPFN; Band-Pass Filter Not; note 1

Note

1. To avoid interference by the video signal, the incoming

baseband signal is filtered. If this filtering is not

required the filter can be switched off.

DEM1

DEM0

DE-EMPHASIS

no de-emphasis (ﬂat)

J17

µs(2)

µs [por](3)

BPFN

DESCRIPTION

mixer input signal ﬁltered by BPF

(after POR)

mixer input signal is not ﬁltered

Slave transmitter mode (bits transmitted from

TDA8745 to microcontroller)

Table 21 Bit PDL; Presence Detector Left; note 1

Note

1. Bit PDL (r7) transmits the current status of the left

channel presence detector. When PDL = 1, no carrier

is found at the currently selected frequency. If bit

PDM (s3) = 0 the left channel audio is muted.

Table 22 Bit PDR; Presence Detector Right; note 1

Note

1. Bit PDR (r6) transmits the current status of the right

channel presence detector. When PDR = 1, no carrier

is found at the currently selected frequency. If bit

PDM (s3) = 0 the right channel audio is muted.

PDL

DESCRIPTION

carrier detected at left channel

no carrier detected at left channel

PDR

DESCRIPTION

carrier detected at right channel

no carrier detected at right channel

Table 23 Bit POR; Power-On Reset; note 1

Note

1. At switching on, or after a power dip on the I2C-bus supply voltage (VP2), an internal signal is generated which resets

the I2C-bus registers to a pre-defined state. If bit POR (r0) = 1, such a situation has occurred since the last time the

read byte was read. After reading, the bit is reset to logic 0.

Table 24 Bits r5 to r1

POR

DESCRIPTION

normal operation

POR generated; power dip detected since last read of POR bit

−

DESCRIPTION

11111

These bits have no function. Although their state is ﬁxed, the microcontroller

should not rely on this because of eventual future use.

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