Rockwell SoniCrafter BT8960 - Manual (Page 32)

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2.0 Functional Description
2.2 Receive Section
Bt8960
Single-Chip 2B1Q Transceiver
N8960DSB
2.2.3.2 Offset
Adjustment
A nonzero DC level on the input can be corrected by a DC offset value
[dc_offset_low, dc_offset_high; 0x26, 0x27] which is subtracted from the input.
The DC offset is a 16-bit number and is programmed via the microcomputer
interface.
2.2.3.3 DC Level Meter The DC level meter provides the monitoring needed for adaptive offset compen-
sation. The offset-adjusted input signal is accumulated over the meter timer inter-
val [meter_low, meter_high; 0x18, 0x19]. The 16 MSBs are placed into the DC
Level Meter Registers [dc_meter_low, dc_meter_high; 0x44, 0x45].
2.2.3.4 Signal Level
Meter
The signal level meter provides the monitoring needed for adjusting the analog
gain circuit located prior to the ADC. This value is accumulated over the meter
timer interval [meter_low, meter_high; 0x18, 0x19]. The 16 MSBs are placed in
the Signal Level Meter Registers [slm_low, slm_high; 1; 0x46, 0x47].
2.2.3.5 Overflow
Detection
and Monitoring
The overflow sensor detects ADC overflows. The overflow monitor counts the
number of overflows, as indicated by the overflow sensor during the meter timer
interval [meter_low, meter_high; 0x18, 0x19]. The counter is limited to 8 bits. In
the case of 256 or more overflows during the measurement interval, the counter
will hold at 255. The counter is loaded into the Overflow Meter Register
[overflow_meter; 0x42] at the end of each measurement interval.
2.2.3.6 Far-End Level
Meter
The far-end level meter monitors the output of the echo canceler. Since the echo
canceler output had the echo of the transmitted signal subtracted from it, it is
called the far-end signal. This value is accumulated over the meter timer interval
[meter_low, meter_high; 0x18, 0x19]. The 16 MSBs are placed into the Far-End
Level Meter Register [felm_low, felm_high; 0x48, 0x49].
2.2.3.7 Far-End Level
Alarm
The result of the far-end level meter is compared to two thresholds. When
exceeded, an interrupt is sent to the microcomputer interface, if enabled. The
threshold is determined by the value in the Far-End High Alarm Threshold Regis-
ters [far_end_high_alarm_th_low, far_end_high_alarm_th_high; 0x30, 0x31] and
the Far-End Low Alarm Threshold Registers [far_end_low_alarm_th_low,
far_end_low_alarm_th_high; 0x32, 0x33].
The interrupts high_felm and low_felm, are bits 2 and 1, respectively of the
IRQ Source Register [irq_source; 0x05]. The interrupts high_felm and low_felm,
can be masked by writing a one to bits 2 and 1, respectively of the Interrupt Mask
Register High [mask_high_reg; 0x03].