ATR4258 Datasheet, PDF (20/38 Pages) ATMEL Corporation – AM/FM RECEIVER IC

AM Noise Blanker
The AM Noise Blanker of the ATR4258 can be activated by bit 5. The noise peak is
detected in the field strength of the first IF and if the disturbance exceeds the level
defined by the bits 85 to 87, the signal is muted at the second IF.
Table 34. AM Noise Blanker Activation
AM Noise Blanker
Off
On
Bit 5
0
1
3-wire Bus Description
Table 35. Sensitivity of AM Noise Blanker
AM Noise Blanker Sensitivity
Low
.....
Normal
...
High
Bit 87
0
...
0
...
1
Bit 86
0
...
1
...
1
Bit 85
0
...
1
...
1
The register settings of the ATR4258 are programmed by a 3-wire bus protocol. The bus
protocol consists of separate commands. A defined number of bits are transmitted
sequentially during each command.
One command is used to program all bits of one register. The different registers avail-
able (see Table 36 on page 22) are addressed by the length of the command (number of
transmitted bits) and by three address bits that are unique for each register of a given
length. 8-bit registers are programmed by 8-bit commands and 24-bit registers are pro-
grammed by 24-bit commands.
Each bus command starts with a rising edge on the enable line (EN) and ends with a
falling edge on EN. EN has to be kept HIGH during the bus command.
The sequence of transmitted bits during one command starts with the LSB of the first
byte and ends with the MSB of the last byte of the register addressed. The DATA is
evaluated at the rising edges of CLK. The number of LOW to HIGH transitions on CLK
during the HIGH period of EN is used to determine the length of the command.
The bus protocol and the register addressing of the ATR4258 are compatible to the
addressing used in the U4256BM. That means both the ATR4258 and U4256BM can
be operated on the same 3-wire bus as shown in the application circuit (Figure 20 on
page 36).
20 ATR4258
4838A–AUDR–10/04