AMIS-53000 Datasheet, PDF (53/99 Pages) AMI SEMICONDUCTOR – Frequency Agile Transceiver

AMIS-53000 Frequency Agile Transceiver
Data Sheet
Table 37: Slice Threshold - 0X1D [29]
Bit Name
Comment
7:0 _{SL_THRESH [7:0]} AM slice threshold in DAC Mode = SL_THRESH*7.8125mV
AM Data Filter and Slice Options
This register contains settings for determining the method of slicing for AM receive mode.
AM_FILTER: Sets the post-detection filter bandwidth for RSSI during AM receive. These filter bandwidths are set for the
corresponding data rates. These filter settings can also be used with custom data rates.
AM_HYST: Sets the amount of hysteresis in the AM slice comparator.
AM_SLICE: Used to select the method for providing a reference to the AM slice comparator. DAC Mode: This is a fixed
threshold level programmed into the slice threshold register.
Average Mode: This is an automatic threshold level where the AMIS-53000 sets the threshold level to the average level of
the RSSI signal. An external capacitor is required on the PEAK pin to set a bandwidth for the low pass filter response of the
averaging circuit. Due to the potential for long strings of 1’s or 0’s in NRZ data this threshold method is not recommended for
use with NRZ data.
Peak Mode: This is similar to the average mode, but only the highest level is determined from the incoming signal and the
AMIS-53000 sets the threshold to a level 6dB lower than the peak value. An external capacitor on the PEAK pin determines a
bleed off (discharge) rate for the peak detector circuit.
Table 38: AM Data Filter and Slice Options - 0X1E [30]
Bit
Name
State Comment
000
001
010
[7:5]
011
AM_FILTER[2:0] ₁₀₀
101
110
111
RSSI filter bandwidth =300Hz
RSSI filter bandwidth = 600Hz
RSSI filter bandwidth = 1.2kHz
RSSI filter bandwidth = 2.4kHz
RSSI filter bandwidth = 4.8kHz
RSSI filter bandwidth = 9.6kHz
RSSI filter bandwidth = 19.2kHz
RSSI filter bandwidth = 38.4kHz
4
NU
00
[3:2]
AM_SLICE[1:0]
01
10
11
DAC mode: Slice threshold set in register 1Bh
Average mode: AM threshold set using averaging filter
Peak detect mode: AM threshold set using peak detector
DAC mode: Slice threshold set in register 1Bh
00
[1:0]
AM_HYST[1:0]
01
10
11
0mV slice hysteresis
25mV slice hysteresis
50mV slice hysteresis
100mV slice hysteresis
FM FFT
The AMIS-53000 receiver uses a FFT function to recover data from a FM/FSK modulated signal when the data rate is higher than
20kbps. The FFT detector uses a two-bit DFFT to demodulate the incoming IF signal. This circuit also uses the same clock recovery
block (CDR) as the AM detector (See Section 6.1.4) to detect the data.
A pattern of 1’s and 0’s is required as a preamble. A SOF is not required unless Manchester encoded data is used, requiring a unique
preamble to bit-align the Manchester decoder to the recovered data.
Setup registers descriptions:
Data Rate- Can be specified in the discrete data rate register, or specified as a 16-bit word for a user defined data rate. (See
Section 7.1.3)
Peak Deviation- The peak deviation register stores the value to be used for both transmit and receive. In the FFT FM receive
mode, this value is used to set-up the FFT bins. (See Sections 6.4.1.5 and 6.4.1.6)
AMI Semiconductor – Aug. 05, Rev. 1.0
53
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