u4255bm ATMEL Corporation, u4255bm Datasheet - Page 7

• Manufacturer Part Number: u4255bm
• Description: Am/fm Receiver
• Manufacturer: ATMEL Corporation

In AM mode (Bits 92 and 93), Bits 81 to 83 set the divide
factor of the AM prescaler
In FM mode and in weather band mode (bit 92), the Bits 81
to 83 set the divide factor at the prescaler
Bit 80 switches between narrow band field strength informa-
tion and wide band field strength information
Bit 79 controls the bandwidth of the lowpass filter of the
MPX output
Rev. A1, 26-Jun-00
Divide by 10
AM Mixer 1
Divide by 6
Divide by 7
Divide by 8
Divide by 4
Sensitivity
Multipath
Field strength from AGC (narrow band)
Divider
Normal
High
Low
Off
Bandwidth MPX Lowpass Filter
Low field strength (wide band)
Narrow Band / Wide Band
Bit 93
Bit 93
1
1
1
1
1
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Field strength
180 kHz
90 kHz
Bit 92
Bit 92
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Bit 84
Bit 84
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Bit 83
Bit 83
0
0
0
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Bit 82
Bit 82
0
0
1
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
Bit 80
Bit 79
Bit 81
Bit 81
0
1
0
1
0
1
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
The stop counter calculates an average center frequency
during the time wich is set by the Bits 73 to 78
The demodulator gain for the weather band mode is set by
the Bits 71 and 72
For soft mute, the MPX signal level will be reduced de-
pending on the input signal strength. Bits 68 to 70 set the
input signal field strength, at which the MPX signal will
be reduced by 3 dB (for soft mute). The absolute value
depends on the IF-gain Bit 89 – 91.
Bit 67 sets the maximum reduction of the MPX signal level
Temperature coefficient setting of FM IF amplifier
64
1
for Stop Signal
Time Window
Temperature Coefficient
Max Value of Soft Mute
(TC) of the IF amplifier
Demodulator Gain in
Weather Band Mode
at high fieldstrength
at low fieldstrength
3.1969 ms
3.1969 ms
.....
Start Soft Mute
30 dB
26 dB
10
20
50
TK 1
TK 2
5
Bit 78 Bit 77 Bit 76 Bit 75 Bit 74 Bit 73
0
1
0
1
U4255BM
Bit 70
0
1
Bit 72
0
0
0
0
1
1
1
1
0
0
1
1
0
1
Bit 69
Bit 67
Bit 66
0
0
1
1
0
0
1
1
0
1
0
1
0
1
Bit 71
Bit 68
0
1
0
1
7 (12)
0
1
0
1
0
1
0
1
1
1