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1 //-----------------------------------------------------------------------------
2 // The way that we connect things when transmitting a command to an ISO
3 // 15693 tag, using 100% modulation only for now.
4 //
5 // Jonathan Westhues, April 2006
6 //-----------------------------------------------------------------------------
7
8 module hi_read_tx(
9 pck0, ck_1356meg, ck_1356megb,
10 pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
11 adc_d, adc_clk,
12 ssp_frame, ssp_din, ssp_dout, ssp_clk,
13 cross_hi, cross_lo,
14 dbg,
15 shallow_modulation
16 );
17 input pck0, ck_1356meg, ck_1356megb;
18 output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
19 input [7:0] adc_d;
20 output adc_clk;
21 input ssp_dout;
22 output ssp_frame, ssp_din, ssp_clk;
23 input cross_hi, cross_lo;
24 output dbg;
25 input shallow_modulation;
26
27 // low frequency outputs, not relevant
28 assign pwr_lo = 1'b0;
29 assign pwr_oe2 = 1'b0;
30
31 // The high-frequency stuff. For now, for testing, just bring out the carrier,
32 // and allow the ARM to modulate it over the SSP.
33 reg pwr_hi;
34 reg pwr_oe1;
35 reg pwr_oe3;
36 reg pwr_oe4;
37
38 always @(ck_1356megb or ssp_dout or shallow_modulation)
39 begin
40 if(shallow_modulation)
41 begin
42 pwr_hi <= ck_1356megb;
43 pwr_oe1 <= 1'b0;
44 pwr_oe3 <= 1'b0;
45 pwr_oe4 <= ssp_dout;
46 end
47 else
48 begin
49 pwr_hi <= ck_1356megb & ~ssp_dout;
50 pwr_oe1 <= 1'b0;
51 pwr_oe3 <= 1'b0;
52 pwr_oe4 <= 1'b0;
53 end
54 end
55
56
57 // Then just divide the 13.56 MHz clock down to produce appropriate clocks
58 // for the synchronous serial port.
59
60 reg [6:0] hi_div_by_128;
61
62 always @(posedge ck_1356meg)
63 hi_div_by_128 <= hi_div_by_128 + 1;
64
65 assign ssp_clk = hi_div_by_128[6];
66
67 reg [2:0] hi_byte_div;
68
69 always @(negedge ssp_clk)
70 hi_byte_div <= hi_byte_div + 1;
71
72 assign ssp_frame = (hi_byte_div == 3'b000);
73
74 assign ssp_din = 1'b0;
75
76 assign dbg = ssp_frame;
77
78 endmodule
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