CRF2 - CRF1 (FM/QPSK PLL Demodulator Offset)

Address

: 20-3D

Type

: R/W

Reset

: 0000 0000

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

CHANNEL 2 or CHANNEL 1 CARRIER RECOVERY FREQUENCY

This register provides access to the instantaneousfrequency of the PLL (2’s complement). If written to, it

will preset the DCO frequency; if read it provides the instantaneousfrequencyoffset of the PLL’s and could

be used for an AFC function.

CETH2 - CETH1 (FM Carrier Level Threshold)

Address

: 21-3E

Type

: R/W

Reset

: 0011 0101

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

CHANNEL 2 or CHANNEL 1 CARRIER-THRESHOLD

These registers, which perform the same function in channel 1 and channel 2, compare the carrier level in

the channel against the threshold value. This level is measured after the channel filter and is relative to the

full scale reference level (0dB).

This is used as part of the validation of an FM signal, if the carrier level is below the threshold, the signal

is considered to be non-valid.

CETH

Threshold (dB)

255

-6

128

-12

64

-18

32

-24

....

....

0

OFF

If CETH is OFF, any carrier level will be accepted.

The reset value is 53, it means a threshold of -20dB.

SQTH2- SQTH1 (FM Squelch Threshold)

Address

: 22-3F

Type

: R/W

Reset

: 0011 1100

bit 7

bit 6

bit 5

bit 4

bit 3

bit 2

bit 1

bit 0

CHANNEL 2 or CHANNEL 1 SQUELCH-THRESHOLD

The squelch detector measures the level of high frequencynoise (>40kHz) and comparesit to the threshold

SQTH. If the level is below this value, the S/N of the FM signal is considered to be acceptable.

Values are given for FM with

±50kHz deviation :

SQTH

S/N (dB)

250

0

119

10

60

15

35

20

22

25

The reset value is 60, it means a SNR of 15dB.

PROGRAMMING THE DEVICE (continued)

STV8203

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