Sundance FC108 v.1.1 - Manual (Page 4)

FC108 - Polyphase filterbank v1.1
Fast
Polyphase filterbank product manual
December 2005 www.sundance.com - 4 -
Data format
The data format is 16-bit integer fixed point and is kept as such for all processing stages.
Please note that the FFT requires normally a 2-bit growth per radix-4 stage, therefore, a scaling
coefficient is user programmable in order to keep the best accuracy as possible.
Other data formats are available upon request.
Ports definitions
Port name Port width Direction Description
clk 1 Input Clock
reset 1 Input Asynchronous reset (active high)
start 1 Input Start signal (active high). Start is asserted for one clock cycle
to start the core. It needs to be asserted once at the beginning
unless the core has been given a stop command. The data on
I_in and Q_in must be valid on the same clock cycle as start
is asserted.
stop 1 Input Stop is asserted for one clock cycle to interrupt the data
processing and put the core in an idle state.
load_filter_taps 1 Output Load filter pass signal (active high). A new filter tap is loaded
to the internal core memory when this signal is active.
I_filter_taps 16 input In phase filter taps bus. The In phase filter taps coefficients
are loaded to the internal core memory via this bus.
Q_filter_taps 16 Input Quadrature phase filter taps bus. The Quadrature phase filter
taps coefficients are loaded to the internal core memory via
this bus.
Filter_taps_addr 15 Input Filter taps address bus. The filter taps will be written to the
address provided on this bus. The three Least Significant Bits
(2 downto 0), represent the tap indexing in a filter. The Most
Significant Bits represent the filter number.
FFT_scaling 4 Input FFT scaling. The scaling schedule is specified with two bits
for every pair of the FFT radix-2 stages. For example, a
scaling schedule for Number of channels=256 could be [2 2 2
3]. When the number of channels is not a power of 4, the
maximum bit growth for the last stage is one bit. For instance,
[0 2 2 2 2] or [1 2 2 2 2] are valid scaling schedules for
N=512, but [2 2 2 2 2] is invalid. The two MSBs of
FFT_scaling can only be 00 or 01.
NB_CH 3 Input Number of channels. This parameter is the number of
channels present in the signal and is equivalent to the FFT
length. The value of NB_CH is log2(number of channels).