//------------------------------------------------------------------------------
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//------------------------------------------------------------------------------
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// uart tasks:
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// uart tasks:
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// send_serial serial transmitter
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// send_serial serial transmitter
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// get_serial serial receiver
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// get_serial serial receiver
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//
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//
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//------------------------------------------------------------------------------
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//------------------------------------------------------------------------------
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/* Serial Parameters used for send_serial task and its callers. */
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/* Serial Parameters used for send_serial task and its callers. */
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`define PARITY_OFF 1'b0
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`define PARITY_OFF 1'b0
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`define PARITY_ON 1'b1
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`define PARITY_ON 1'b1
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`define PARITY_ODD 1'b0
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`define PARITY_ODD 1'b0
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`define PARITY_EVEN 1'b1
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`define PARITY_EVEN 1'b1
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`define NSTOPS_1 1'b0
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`define NSTOPS_1 1'b0
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`define NSTOPS_2 1'b1
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`define NSTOPS_2 1'b1
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`define BAUD_115200 3'b000
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`define BAUD_115200 3'b000
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`define BAUD_38400 3'b001
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`define BAUD_38400 3'b001
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`define BAUD_28800 3'b010
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`define BAUD_28800 3'b010
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`define BAUD_19200 3'b011
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`define BAUD_19200 3'b011
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`define BAUD_9600 3'b100
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`define BAUD_9600 3'b100
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`define BAUD_4800 3'b101
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`define BAUD_4800 3'b101
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`define BAUD_2400 3'b110
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`define BAUD_2400 3'b110
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`define BAUD_1200 3'b111
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`define BAUD_1200 3'b111
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`define NBITS_7 1'b0
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`define NBITS_7 1'b0
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`define NBITS_8 1'b1
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`define NBITS_8 1'b1
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// constants for status from get_serial task
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// constants for status from get_serial task
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`define RECEIVE_RESULT_OK 4'b1000
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`define RECEIVE_RESULT_OK 4'b1000
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`define RECEIVE_RESULT_FALSESTART 4'b0001
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`define RECEIVE_RESULT_FALSESTART 4'b0001
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`define RECEIVE_RESULT_BADPARITY 4'b0010
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`define RECEIVE_RESULT_BADPARITY 4'b0010
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`define RECEIVE_RESULT_BADSTOP 4'b0100
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`define RECEIVE_RESULT_BADSTOP 4'b0100
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// uart tasks global interfaces signals
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// uart tasks global interfaces signals
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reg serial_out; // transmit serial output
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reg serial_out; // transmit serial output
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reg serial_in; // receive serial input
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reg serial_in; // receive serial input
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reg [7:0] get_serial_data; // data received from serial
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reg [7:0] get_serial_data; // data received from serial
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reg [7:0] get_serial_status; // status of receive operation
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reg [7:0] get_serial_status; // status of receive operation
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//------------------------------------------------------------------------------
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//------------------------------------------------------------------------------
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// uart transmit task
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// uart transmit task
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//
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//
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// usage:
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// usage:
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// send_serial (data, baud_rate, parity_type, parity_on, stop_bits_num,
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// send_serial (data, baud_rate, parity_type, parity_on, stop_bits_num,
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// data_bit_num, baud_error);
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// data_bit_num, baud_error);
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// where:
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// where:
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// data data character for transmission
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// data data character for transmission
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// parity_type this is a flag indicating that parity should be even
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// parity_type this is a flag indicating that parity should be even
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// (either 'PARITY_ODD or 'PARITY_EVEN)
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// (either 'PARITY_ODD or 'PARITY_EVEN)
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// parity_on indicates that the parity is used
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// parity_on indicates that the parity is used
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// (either 'PARITY_OFF or 'PARITY_ON)
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// (either 'PARITY_OFF or 'PARITY_ON)
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// stop_bits_num number of stop bits (either NSTOPS_1 or NSTOPS_2)
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// stop_bits_num number of stop bits (either NSTOPS_1 or NSTOPS_2)
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// data_bit_num number of data bits (either NBITS_7 or NBITS_8)
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// data_bit_num number of data bits (either NBITS_7 or NBITS_8)
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// baud_error baud error in precentage (-5 is -5%)
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// baud_error baud error in precentage (-5 is -5%)
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//
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//
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task send_serial;
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task send_serial;
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// task input parameters
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// task input parameters
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input [7:0] inputchar;
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input [7:0] inputchar;
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input baud;
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input baud;
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input paritytype;
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input paritytype;
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input parityenable;
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input parityenable;
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input nstops;
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input nstops;
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input nbits;
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input nbits;
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input baud_error_factor;
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input baud_error_factor;
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// internal registers
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// internal registers
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reg nbits;
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reg nbits;
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reg parityenable;
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reg parityenable;
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reg paritytype;
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reg paritytype;
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reg [1:0] baud;
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reg [1:0] baud;
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reg nstops;
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reg nstops;
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integer baud_error_factor; // e.g. +5 means 5% too fast and -5 means 5% too slow
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integer baud_error_factor; // e.g. +5 means 5% too fast and -5 means 5% too slow
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reg [7:0] char;
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reg [7:0] char;
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reg [7:0] disp_char;
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reg [7:0] disp_char;
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reg parity_bit;
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reg parity_bit;
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integer bit_time;
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integer bit_time;
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integer num_of_bits;
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integer num_of_bits;
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// task implementation
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// task implementation
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begin
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begin
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char = inputchar;
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char = inputchar;
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parity_bit = 1'b0;
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parity_bit = 1'b0;
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// calculate bit time from input baud rate - this assumes a simulation resolution of 1ns
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// calculate bit time from input baud rate - this assumes a simulation resolution of 1ns
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case (baud)
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case (baud)
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`BAUD_115200: bit_time = 1000000000/(115200 + 1152*baud_error_factor);
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`BAUD_115200: bit_time = 1000000000/(115200 + 1152*baud_error_factor);
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// `BAUD_115200: bit_time = 40000000000/(115200 + 1152*baud_error_factor);
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// `BAUD_115200: bit_time = 40000000000/(115200 + 1152*baud_error_factor);
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`BAUD_38400: bit_time = 1000000000/(38400 + 384*baud_error_factor);
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`BAUD_38400: bit_time = 1000000000/(38400 + 384*baud_error_factor);
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`BAUD_28800: bit_time = 1000000000/(28800 + 288*baud_error_factor);
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`BAUD_28800: bit_time = 1000000000/(28800 + 288*baud_error_factor);
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`BAUD_19200: bit_time = 1000000000/(19200 + 192*baud_error_factor);
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`BAUD_19200: bit_time = 1000000000/(19200 + 192*baud_error_factor);
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`BAUD_9600: bit_time = 1000000000/(9600 + 96*baud_error_factor);
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`BAUD_9600: bit_time = 1000000000/(9600 + 96*baud_error_factor);
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`BAUD_4800: bit_time = 1000000000/(4800 + 48*baud_error_factor);
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`BAUD_4800: bit_time = 1000000000/(4800 + 48*baud_error_factor);
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`BAUD_2400: bit_time = 1000000000/(2400 + 24*baud_error_factor);
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`BAUD_2400: bit_time = 1000000000/(2400 + 24*baud_error_factor);
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`BAUD_1200: bit_time = 1000000000/(1200 + 12*baud_error_factor);
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`BAUD_1200: bit_time = 1000000000/(1200 + 12*baud_error_factor);
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endcase
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endcase
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// display info
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// display info
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disp_char = (char >= 8'h20) ? char : 8'hb0;
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disp_char = (char >= 8'h20) ? char : 8'hb0;
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$display ("Sending character 0x%h (\"%c\"), at %0d baud (err=%0d), %0d bits, %0s parity, %0d stops",
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$display ("Sending character 0x%h (\"%c\"), at %0d baud (err=%0d), %0d bits, %0s parity, %0d stops",
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(nbits == `NBITS_7) ? (char & 8'h7f) : char,
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(nbits == `NBITS_7) ? (char & 8'h7f) : char,
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(nbits == `NBITS_7) ? (disp_char & 8'h7f) : disp_char,
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(nbits == `NBITS_7) ? (disp_char & 8'h7f) : disp_char,
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1000000000/bit_time,
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1000000000/bit_time,
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baud_error_factor,
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baud_error_factor,
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(nbits == `NBITS_7) ? 7 : 8,
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(nbits == `NBITS_7) ? 7 : 8,
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(parityenable == `PARITY_OFF) ? "NONE" : (paritytype == `PARITY_EVEN) ? "EVEN" : "ODD",
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(parityenable == `PARITY_OFF) ? "NONE" : (paritytype == `PARITY_EVEN) ? "EVEN" : "ODD",
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(nstops == `NSTOPS_1) ? 1 : 2
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(nstops == `NSTOPS_1) ? 1 : 2
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);
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);
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// Start bit
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// Start bit
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serial_out = 1'b0; // Start bit.
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serial_out = 1'b0; // Start bit.
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#(bit_time);
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#(bit_time);
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// Output data bits
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// Output data bits
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num_of_bits = (nbits == `NBITS_7) ? 7 : 8;
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num_of_bits = (nbits == `NBITS_7) ? 7 : 8;
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repeat (num_of_bits)
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repeat (num_of_bits)
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begin
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begin
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serial_out = char[0];
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serial_out = char[0];
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#(bit_time);
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#(bit_time);
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char = {1'b0, char[7:1]};
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char = {1'b0, char[7:1]};
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end
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end
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// check if parity is enabled
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// check if parity is enabled
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if (parityenable == `PARITY_ON) begin
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if (parityenable == `PARITY_ON) begin
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parity_bit = (nbits == `NBITS_7) ? ^inputchar[6:0] : ^inputchar[7:0];
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parity_bit = (nbits == `NBITS_7) ? ^inputchar[6:0] : ^inputchar[7:0];
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// even parity
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// even parity
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if (paritytype == `PARITY_ODD)
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if (paritytype == `PARITY_ODD)
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parity_bit = ~parity_bit;
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parity_bit = ~parity_bit;
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serial_out = parity_bit;
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serial_out = parity_bit;
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#(bit_time);
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#(bit_time);
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end
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end
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// Stop bit.
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// Stop bit.
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serial_out = 1'b1;
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serial_out = 1'b1;
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#(bit_time);
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#(bit_time);
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// Second stop bit
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// Second stop bit
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if (nstops)
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if (nstops)
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#(bit_time);
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#(bit_time);
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end
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end
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endtask
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endtask
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//------------------------------------------------------------------------------
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//------------------------------------------------------------------------------
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// uart receive task
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// uart receive task
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//
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//
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// usage:
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// usage:
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// get_serial (baud_rate, parity_type, parity_on, stop_bits_num, data_bit_num);
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// get_serial (baud_rate, parity_type, parity_on, stop_bits_num, data_bit_num);
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// where:
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// where:
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// data data character for transmission
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// data data character for transmission
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// parity_type this is a flag indicating that parity should be even
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// parity_type this is a flag indicating that parity should be even
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// (either 'PARITY_ODD or 'PARITY_EVEN)
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// (either 'PARITY_ODD or 'PARITY_EVEN)
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// parity_on indicates that the parity is used
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// parity_on indicates that the parity is used
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// (either 'PARITY_OFF or 'PARITY_ON)
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// (either 'PARITY_OFF or 'PARITY_ON)
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// stop_bits_num number of stop bits (either NSTOPS_1 or NSTOPS_2)
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// stop_bits_num number of stop bits (either NSTOPS_1 or NSTOPS_2)
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// data_bit_num number of data bits (either NBITS_7 or NBITS_8)
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// data_bit_num number of data bits (either NBITS_7 or NBITS_8)
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//
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//
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task get_serial;
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task get_serial;
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// input parameters
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// input parameters
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input baud;
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input baud;
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input paritytype;
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input paritytype;
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input parityenable;
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input parityenable;
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input nstops;
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input nstops;
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input nbits;
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input nbits;
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// internal registers
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// internal registers
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reg nbits;
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reg nbits;
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reg parityenable;
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reg parityenable;
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reg paritytype;
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reg paritytype;
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reg [1:0] baud;
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reg [1:0] baud;
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reg nstops;
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reg nstops;
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integer bit_time;
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integer bit_time;
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reg expected_parity;
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reg expected_parity;
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integer num_of_bits;
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integer num_of_bits;
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// task implementation
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// task implementation
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begin
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begin
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// init receive globals
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// init receive globals
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get_serial_status = 0;
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get_serial_status = 0;
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get_serial_data = 0;
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get_serial_data = 0;
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// calculate bit time from input baud rate - this assumes a simulation resolution of 1ns
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// calculate bit time from input baud rate - this assumes a simulation resolution of 1ns
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case (baud)
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case (baud)
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`BAUD_115200: bit_time = 1000000000/115200;
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`BAUD_115200: bit_time = 1000000000/115200;
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`BAUD_38400: bit_time = 1000000000/38400;
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`BAUD_38400: bit_time = 1000000000/38400;
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`BAUD_28800: bit_time = 1000000000/28800;
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`BAUD_28800: bit_time = 1000000000/28800;
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`BAUD_19200: bit_time = 1000000000/19200;
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`BAUD_19200: bit_time = 1000000000/19200;
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`BAUD_9600: bit_time = 1000000000/9600;
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`BAUD_9600: bit_time = 1000000000/9600;
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`BAUD_4800: bit_time = 1000000000/4800;
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`BAUD_4800: bit_time = 1000000000/4800;
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`BAUD_2400: bit_time = 1000000000/2400;
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`BAUD_2400: bit_time = 1000000000/2400;
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`BAUD_1200: bit_time = 1000000000/1200;
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`BAUD_1200: bit_time = 1000000000/1200;
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endcase
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endcase
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// Assume OK until bad things happen.
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// Assume OK until bad things happen.
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get_serial_status = `RECEIVE_RESULT_OK;
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get_serial_status = `RECEIVE_RESULT_OK;
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// wait for start bit edge
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// wait for start bit edge
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@(negedge serial_in);
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@(negedge serial_in);
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// wait till center of start bit
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// wait till center of start bit
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#(bit_time/2);
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#(bit_time/2);
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// make sure its really a start bit
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// make sure its really a start bit
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if (serial_in != 0)
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if (serial_in != 0)
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get_serial_status = get_serial_status | `RECEIVE_RESULT_FALSESTART;
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get_serial_status = get_serial_status | `RECEIVE_RESULT_FALSESTART;
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else
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else
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begin
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begin
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// get all the data bits (7 or 8)
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// get all the data bits (7 or 8)
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num_of_bits = (nbits == `NBITS_7) ? 7 : 8;
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num_of_bits = (nbits == `NBITS_7) ? 7 : 8;
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repeat (num_of_bits)
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repeat (num_of_bits)
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begin
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begin
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// wait till center
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// wait till center
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#(bit_time);
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#(bit_time);
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// sample a data bit
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// sample a data bit
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get_serial_data = {serial_in, get_serial_data[7:1]};
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get_serial_data = {serial_in, get_serial_data[7:1]};
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end
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end
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// If we are only expecting 7 bits, go ahead and right-justify what we have
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// If we are only expecting 7 bits, go ahead and right-justify what we have
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if (nbits == `NBITS_7)
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if (nbits == `NBITS_7)
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get_serial_data = {1'b0, get_serial_data[7:1]};
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get_serial_data = {1'b0, get_serial_data[7:1]};
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// wait for next bit to start
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// wait for next bit to start
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#(bit_time);
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#(bit_time);
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// now, we have either a parity bit, or a stop bit
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// now, we have either a parity bit, or a stop bit
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if (parityenable == `PARITY_ON) begin
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if (parityenable == `PARITY_ON) begin
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if (paritytype == `PARITY_EVEN)
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if (paritytype == `PARITY_EVEN)
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expected_parity = (nbits == `NBITS_7) ? (^get_serial_data[6:0]) :
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expected_parity = (nbits == `NBITS_7) ? (^get_serial_data[6:0]) :
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(^get_serial_data[7:0]);
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(^get_serial_data[7:0]);
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else
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else
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expected_parity = (nbits == `NBITS_7) ? (~(^get_serial_data[6:0])) :
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expected_parity = (nbits == `NBITS_7) ? (~(^get_serial_data[6:0])) :
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(~(^get_serial_data[7:0]));
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(~(^get_serial_data[7:0]));
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if (expected_parity != serial_in)
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if (expected_parity != serial_in)
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get_serial_status = get_serial_status | `RECEIVE_RESULT_BADPARITY;
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get_serial_status = get_serial_status | `RECEIVE_RESULT_BADPARITY;
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end
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end
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// wait for either 1 or 2 stop bits
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// wait for either 1 or 2 stop bits
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else begin
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else begin
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// this is a stop bit.
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// this is a stop bit.
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if (serial_in != 1)
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if (serial_in != 1)
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get_serial_status = get_serial_status | `RECEIVE_RESULT_BADSTOP;
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get_serial_status = get_serial_status | `RECEIVE_RESULT_BADSTOP;
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else
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else
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// that was cool. if 2 stops, then do this again
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// that was cool. if 2 stops, then do this again
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if (nstops)
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if (nstops)
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begin
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begin
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#(bit_time);
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#(bit_time);
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if (serial_in != 1)
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if (serial_in != 1)
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get_serial_status = get_serial_status | `RECEIVE_RESULT_BADSTOP;
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get_serial_status = get_serial_status | `RECEIVE_RESULT_BADSTOP;
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end
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end
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#(bit_time/2);
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end
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end
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end
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end
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end
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end
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endtask
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endtask
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