STV8203 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STV8203' PDF : 31 Pages View PDF
STV8203
PROGRAMMING THE DEVICE (continued)
AGCS (AGC Control and Status for ADC)
Address
Type
Reset
: 12
: R/W
: 0100 00XX
bit 7
0
bit 6
bit 5
bit 4
AGC-ERR
bit 3
bit 2
bit 1
SIG-OVR
bit 0
SIG-UND
AGC-ERR : Gain Control Signal of amplifier before ADC. There are 32 steps of 1.25dB.
AGC-ERR [6:2]
Gain (dB)
00000
0
00001
1.25
.....
.....
11110
37.50
11111
38.75
When AGC_CMD = 0, AGC-ERR can be read thus indicating the input level. It can also be
written to thus presetting the AGC level which will then adjust itself to the final value. When
AGC_CMD = 1, the AGC is off and thus writing to AGC-ERR directly controls the AGC
amplifier gain. Reading AGC_ERR just confirms the fixed value.
SIG-OVR
SIG-UND
: 1 = agc overloaded - signal too BIG
1 = agc under loaded - signal too SMALL
When the AGC is in automatic mode (agc_cmd=0), bit 0 indicates if the input signal is too
small and bit 1 if the AGC is too big. These bits could be used when setting the input level
to the STV8203.
IAGCR (Internal AGC Reference for QPSK)
Address
Type
Reset
: 14
: R/W
: 1000 1000
bit 7
bit 6
bit 5
bit 4
bit 3
IAGC-REF
bit 2
bit 1
bit 0
Sets the mean value of the internal AGC, used for QPSK demodulation. The default setting corresponds
to half full scale amplitude at the PLL input.
IAGCC (Internal AGC Time Constant for QPSK)
Address
Type
Reset
: 15
: R/W
: 0000 0011
bit 7
IAGC-OFF
bit 6
0
bit 5
0
bit 4
0
bit 3
0
bit 2
bit 1
IAGC-CST
bit 0
IAGC-OFF : 1 = Internal agc = off
Only enabled when AUTOSTANDARD is off. Normally , the internal AGC should be OFF for
FM and ON for QPSK.
This bit is controlled by AUTOSTANDARD when this function is activated.
IAGC-CST : Internal AGC Programmable Step Constant.
Set the internal AGC time constant; the compromise is between fast settling time (for the
quickest Nicam identification) and noise immunity. The control range is about 45dB divided
into 0.2dB steps. These bits control the time per step (values given for QPSK mode) :
AGC-CST [2:0]
000
Step time (µs)
703
Time Response (ms)
105
001
352
53
.....
.....
.....
111
5.5
0.82
22/31
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