1 files changed, 82 insertions, 0 deletions

diff --git a/jtag_uart.sv b/jtag_uart.sv
new file mode 100644
index 0000000..ddb5ecb
--- /dev/null
+++ b/jtag_uart.sv
@@ -0,0 +1,82 @@
+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