QF1DA512-DK Quickfilter Technologies LLC, QF1DA512-DK Datasheet - Page 16

• Manufacturer Part Number: QF1DA512-DK
• Description: KIT DEV FOR QF1DA512
• Manufacturer: Quickfilter Technologies LLC
• Series: SavFIRe™r

Specifications of QF1DA512-DK

• Main Purpose: Filters, Digital Filter Design
• Embedded: Yes, ASIC
• Utilized Ic / Part: QF1Da512
• Primary Attributes: 1 512 Tap FIR Filter, 12 ~ 24 Bit
• Secondary Attributes: Quickfilter Software Design Tool GUI, Works from 10 ~ 500ksps ADC Data Rates
• For Use With: WM2582 - EVALDI EARBUDS TYPE Y686-1006 - BOARD MSP-MOJO + EXPANSION HEADR
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 686-1010

The QF1Da512 supports data widths in the range of 12 and 24 bits, and headers of up to 8 bits.
The format of the input data stream is specified in the HD_OFFSET (address 09h), HD_SIZE (address 0Ah), DATA_OFFSET (address
000Dh), and the DATA_SIZE (address 000Eh) registers. These registers set the header offset, header size, data offset, and data size
respectively of the individual data sample. This allows for a large number of different data formats. Additionally, if the sample data
contains a data valid qualifier, this field can be masked by configuring the HD_MASK, address 0Bh and HD_VALUE, address 0Ch
registers. The filtering of the sample will occur only if a logical and of the header value and HD_MASK matches HD_VALUE , address
0Ch, otherwise the raw sample data is passed directly through to the dSDO pin unfiltered.
When configured for FILTER mode, FILT_EN bit set to „1‟in the CONTROL register (03h), the output stream on the dSDO pin will have
the same format as the input stream coming in on the dSDI pin. The header data is passed directly through to the dSDO pin while the
filtered data has a latency associated with it due to the properties of the FIR filter. If no filtering is being done (data valid qualifier in
header does not match HD_VALUE) coincident header and data will be passed through for possible use down-stream of the
QF1Da512 device.
When averaging and / or down sampling is active, the data rate will be the same as the incoming data rate, but the number of valid
samples will be reduced by the averaging / down sampling rate.
Data Passthrough
Sometimes it is required to pass-through the data present at dSDI directly to the dSDO output, for example when passing configuration
data back from an ADC to the host controller. The data pass-through bit, DIN_PT, in the CONTROL register (03h), will force this to
occur when it is set to 1. In this mode dSDO follows dSDI immediately, there is no clocking required. This control bit overrides all other
settings for dSDO functionality (see next section) and should be set to 0 for either configuration mode or data filtering.
8
Downconverter
The QF1Da512 provides the capability to down-sample the incoming data samples. The divider ratio is any integer value and ranges
from 1 (no down-sampling) to 256. The value is selected in the DECIMATE register (address 08h). In addition to down-sampling and
“throwing away” the intermediate samples, and option is provided to average the samples and forward the averaged value to the
downstream FIR filter. The averaging block effectively adds up N samples, where N is the down-sampling rate, then divides by a power
of 2 by right shifting the result. Note that if averaging is enabled with a down-sampling rate that is not a power of 2, system gain will be
affected. The averaging block always divides by the next highest power of 2 when a non power of 2 down-sampling rate is detected.
Rev A8 January 7, 2009
DIGITAL DOWN SAMPLING
Ouput
Input
Header = 01100010,
Data valid qualifier bits are the two least significant bits, therefore hd_mask = 00000011
The data to be filtered has a data qualifier of 10, therefore the hd_value = 00000010
Data is filtered when a logical and of the header and hd_mask = hd_value
hd_mask
hd_value
hd_off
(011000010) AND (00000011) = (00000010) = hd_value = filter this data!
set
Figure 9: Data Header Masking Example
PRELIMINARY DATA SHEET
0
0 0 0 0 0 0 1 1
0 0 0 0 0 0 1 0
0 1 1 0 0 0 1 0
data_offset
1 1 0 0 0 1 0
hd_size
16
filter this data!
previously filtered data
data_size
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QF1Da512