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/** CIC Multichannel
Generic multichannel Cascaded-Integrator-Comb filter comprised of:
- Double Integrator (DI) per channel
- Multichannel Serializer sampling the output of all DIs into a shift-chain
at a rate defined by cic_base_per
- (Optional configurable delay chain)
- Cascaded Differentiator and post-filter (CC Filter) with barrel shifter
sampled at a rate defined by cc_samp_per
- CIC timing generator
- Shift-chain tap of the DI serialized stream
+-------------------------------------+
| +-----+ +---+ |
in[0]--->D INT+---> | +-------------> di_sr_out
| +-----+ | S | | |
| | E | | +------+ |
| +-----+ | R | | | | |
in[1]--->D INT+---> I +-[][][]--+-->CCFILT+---> cc_sr_out
| +-----+ | A | SHIFT | | |
| | L | +---^--+ |
| +-----+ | | | |
in[N]--->D INT+---> | | |
| +-----+ +-^-+ | |
| | | |
+-------------------------------------+
| |
cic_sample + + cc_sample
*/
module cic_multichannel #(
parameter n_chan=12,
// DI parameters
parameter di_dwi=16, // data width
parameter di_rwi=32, // result width
// Difference between above two widths should be N*log2 of the maximum number
// of samples per CIC sample, where N=2 is the order of the CIC filter
parameter di_noise_bits=4, // Number of noise bits to discard at the output of Double Integrator.
// This depends on the SNR of the inputs and the CIC sample rate
parameter shift_delay=0, // Optional shifter between Integrator and Comb. A value of 0 disables shifter
parameter cc_outw=20, // CCFilt output width; Must be 20 if using half-band filter
parameter cc_halfband=1,
parameter cc_use_delay=0, // Match pipeline length of filt_halfband=1
parameter cc_shift_base=0, // Bits to discard from previous acc step
parameter cc_shift_wi=4
) (
// Incoming stream
input clk,
input reset,
input stb_in, // Strobe signal for input samples
input [n_chan*di_dwi-1:0] d_in, // Flattened array of unprocessed data streams. CH0 in LSBs
input cic_sample, // CIC base sampling signal
// CC Filter controls
input cc_sample, // CCFilt sampling signal
input [cc_shift_wi-1:0] cc_shift, // controls scaling of filter result
// Post-integrator conveyor belt tap
output di_stb_out,
output [di_rwi-1:0] di_sr_out,
// Post-CC filter conveyor belt out
output cc_stb_out,
output signed [cc_outw-1:0] cc_sr_out
);
// Synchronize reset
reg [1:0] reset_r=0;
always @(posedge clk) begin
reset_r <= {reset_r[0],reset};
end
// ------
// Double Integrator per channel
// ------
wire [n_chan*di_rwi-1:0] di_out;
genvar ch_id;
generate for (ch_id=0; ch_id < n_chan; ch_id=ch_id+1) begin : g_d_int
double_inte_smp #(
.dwi (di_dwi),
.dwo (di_rwi))
i_double_inte (
.clk (clk),
.reset (reset_r[1]),
.stb_in (stb_in),
.in (d_in[(ch_id+1)*di_dwi-1:ch_id*di_dwi]),
.out (di_out[(ch_id+1)*di_rwi-1:ch_id*di_rwi])
);
end endgenerate
// ------
// Multichannel serializer/conveyor belt generator
// ------
wire [di_rwi-1:0] sr_out_l;
wire stb_out_l;
serializer_multichannel #(
.n_chan (n_chan),
.dw (di_rwi))
i_serializer_multich (
.clk (clk),
.sample_in (cic_sample),
.data_in (di_out),
.gate_out (stb_out_l),
.stream_out (sr_out_l)
);
// ------
// Optional shift-based delay
// ------
wire [di_rwi-1:0] sr_out_shift;
wire stb_out_shift, stb_out_shift_l;
reg_delay #(
.dw (di_rwi+1),
.len (shift_delay*n_chan))
i_shift_delay (
.clk (clk),
.reset (reset),
.gate (stb_out_l), // Shift at line-rate
.din ({sr_out_l, stb_out_l}),
.dout ({sr_out_shift, stb_out_shift_l})
);
assign stb_out_shift = stb_out_shift_l & stb_out_l;
// Pre-comb conveyor-belt tap
assign di_stb_out = stb_out_shift;
assign di_sr_out = sr_out_shift;
// ------
// Cascaded differentiator and post-filter
// ------
`ifdef SIMULATE
// Enforces correct parameter settings
initial begin
if (cc_halfband && cc_outw != 20) begin
$display("ERROR: Output width of CC filt must be 20 when using the Half-Band filter");
$finish;
end
end
`endif
ccfilt #(
.dw (di_rwi-di_noise_bits),
.outw (cc_outw),
.shift_wi (cc_shift_wi),
.shift_base (cc_shift_base),
.dsr_len (n_chan),
.use_hb (cc_halfband),
.use_delay (cc_use_delay))
i_ccfilt
(
.clk (clk),
.reset (reset),
.sr_in (sr_out_shift[di_rwi-1:(di_noise_bits)]), // Discard noisy LSBs
.sr_valid (stb_out_shift&cc_sample),
.shift (cc_shift),
.result (cc_sr_out), // signed filtered and scaled result
.strobe (cc_stb_out)
);
endmodule
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