input pck0, ck_1356meg, ck_1356megb;
output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
input [7:0] adc_d;
- output adc_clk;
+ output adc_clk, ssp_frame, ssp_din;
input ssp_dout;
- output ssp_frame, ssp_din, ssp_clk;
+ output ssp_clk;
input cross_hi, cross_lo;
output dbg;
input xcorr_is_848, snoop;
assign pwr_oe3 = 1'b0;
assign pwr_oe4 = 1'b0;
-(* clock_signal = "yes" *) reg fc_div_2;
+wire adc_clk = ck_1356megb;
+
+reg fc_div_2;
always @(negedge ck_1356megb)
fc_div_2 <= fc_div_2 + 1;
-(* clock_signal = "yes" *) reg adc_clk;
-always @(xcorr_is_848, ck_1356megb, fc_div_2)
-if (xcorr_is_848)
- // The subcarrier frequency is fc/16; we will sample at fc, so that
- // means the subcarrier is 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 ...
- adc_clk <= ck_1356megb;
-else
- // The subcarrier frequency is fc/32; we will sample at fc/2, and
- // the subcarrier will look identical.
- adc_clk <= fc_div_2;
-
-
// When we're a reader, we just need to do the BPSK demod; but when we're an
// eavesdropper, we also need to pick out the commands sent by the reader,
// using AM. Do this the same way that we do it for the simulated tag.
reg ssp_frame;
+always @(negedge adc_clk)
+begin
+ if (xcorr_is_848 | fc_div_2)
+ corr_i_cnt <= corr_i_cnt + 1;
+end
+
// ADC data appears on the rising edge, so sample it on the falling edge
always @(negedge adc_clk)
begin
- corr_i_cnt <= corr_i_cnt + 1;
-
// These are the correlators: we correlate against in-phase and quadrature
// versions of our reference signal, and keep the (signed) result to
// send out later over the SSP.
- if(corr_i_cnt == 7'd0)
+ if(corr_i_cnt == 6'd0)
begin
if(snoop)
- begin
- // 7 most significant bits of tag signal (signed), 1 bit reader signal:
- corr_i_out <= {corr_i_accum[13:7], after_hysteresis_prev_prev};
- corr_q_out <= {corr_q_accum[13:7], after_hysteresis_prev};
- after_hysteresis_prev_prev <= after_hysteresis;
- end
+ begin
+ // Send only 7 most significant bits of tag signal (signed), LSB is reader signal:
+ corr_i_out <= {corr_i_accum[13:7], after_hysteresis_prev_prev};
+ corr_q_out <= {corr_q_accum[13:7], after_hysteresis_prev};
+ after_hysteresis_prev_prev <= after_hysteresis;
+ end
else
- begin
- // 8 most significant bits of tag signal
- corr_i_out <= corr_i_accum[13:6];
- corr_q_out <= corr_q_accum[13:6];
- end
+ begin
+ // 8 most significant bits of tag signal
+ corr_i_out <= corr_i_accum[13:6];
+ corr_q_out <= corr_q_accum[13:6];
+ end
corr_i_accum <= adc_d;
corr_q_accum <= adc_d;
// The logic in hi_simulate.v reports 4 samples per bit. We report two
// (I, Q) pairs per bit, so we should do 2 samples per pair.
- if(corr_i_cnt == 6'd31)
+ if(corr_i_cnt == 6'd32)
after_hysteresis_prev <= after_hysteresis;
// Then the result from last time is serialized and send out to the ARM.