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module jtag_uart
#( INSTANCE = 0
, RX_FIFO_BITS = 6
, TX_FIFO_BITS = 6
)
( input bit clk
, input bit reset
, input bit rx_ready `define rx_ready $past(rx_ready)
, output bit rx_valid
, output bit [7:0] rx_data
, output bit tx_ready
, input bit tx_valid `define tx_valid $past(tx_valid)
, input bit [7:0] tx_data `define tx_data $past(tx_data)
);
`ifdef SYNTHESIS
alt_jtag_atlantic
#( .INSTANCE_ID(INSTANCE)
, .LOG2_RXFIFO_DEPTH(RX_FIFO_BITS)
, .LOG2_TXFIFO_DEPTH(TX_FIFO_BITS)
, .SLD_AUTO_INSTANCE_INDEX("NO")
) real_jtag
( .clk(clk)
, .rst_n(!reset)
, .r_dat(tx_data)
, .r_val(tx_valid)
, .r_ena(tx_ready)
, .t_dat(rx_data)
, .t_dav(rx_ready)
, .t_ena(rx_valid)
);
`else
bit [7:0] sim_rx_rom [0:(1<<16)-1];
initial $readmemh("jtag_uart.hex", sim_rx_rom);
bit [15:0] sim_rx_addr;
bit tx_b_valid;
bit [7:0] tx_b_data;
always_ff @(posedge clk) begin
if (reset) begin
rx_valid = 0;
tx_ready = 0;
sim_rx_addr = 0;
tx_b_valid = 0;
end else begin
automatic bit [7:0] sim_rx_data = sim_rx_rom[sim_rx_addr];
// RX logic
if (`rx_ready) rx_valid = 0;
if (!rx_valid && (sim_rx_data != 0)) begin
`ifdef JTAG_UART_LOCAL_ECHO
$write("%s", sim_rx_data);
`endif
rx_valid = 1;
rx_data = sim_rx_data;
sim_rx_addr = sim_rx_addr + 1;
end
// TX logic
if (tx_ready && `tx_valid) begin
tx_b_valid = 1;
tx_b_data = `tx_data;
end
if (tx_b_valid) begin
$write("%s", tx_b_data);
tx_b_valid = 0;
end
tx_ready = !tx_b_valid;
end
end
`endif
endmodule
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