From 0553c4839c06011bd044f69b4913e5c793fdd2ec Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sun, 27 Feb 2022 17:21:05 -0800
Subject: Initial commit.

---
 hdl/command_parser.sv | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 hdl/command_parser.sv

(limited to 'hdl/command_parser.sv')

diff --git a/hdl/command_parser.sv b/hdl/command_parser.sv
new file mode 100644
index 0000000..5c49db9
--- /dev/null
+++ b/hdl/command_parser.sv
@@ -0,0 +1,109 @@
+`include "defs.svh"
+
+module command_parser
+    #(  TAG = 0
+    ) ( input   bit         clock
+    ,   input   bit         reset
+
+    ,   output  bit         uart_ready
+    ,   input   bit         uart_valid
+    ,   input   uart_byte_t uart_data
+
+    ,   input   bit         echo_ready
+    ,   output  bit         echo_valid
+    ,   output  uart_byte_t echo_data
+
+    ,   input   bit             command_ready
+    ,   output  bit             command_valid
+    ,   output  ram_command_t   command_data
+    );
+
+    bit         input_byte_valid;
+    uart_byte_t input_byte;
+
+    (* syn_encoding = "one-hot" *) enum int unsigned
+        {   READ_ADDRESS_OR_COMMAND
+        ,   READ_DATA
+        } state;
+
+    always @(posedge clock) begin
+        if (reset) begin
+            uart_ready = 0;
+            command_valid = 0;
+            input_byte_valid = 0;
+            input_byte = 0;
+            state = state.first;
+        end else begin
+            if (echo_ready) echo_valid = 0;
+            if (command_ready && command_valid) begin
+                command_valid = 0;
+                command_data.address = 0;
+                command_data.write = 0;
+                for (int i = 0; i < `RAM_LINE_WORDS; i = i + 1) begin
+                    command_data.data[i] = 0;
+                    command_data.mask[i] = ~0;
+                end
+                command_data.tag = TAG;
+            end
+            if (uart_ready && uart_valid) begin
+                echo_valid = 1;
+                echo_data = uart_data;
+                input_byte_valid = 1;
+                input_byte = uart_data;
+            end
+
+            if (!command_valid && input_byte_valid) begin
+                case (state)
+
+                READ_ADDRESS_OR_COMMAND: begin
+                    if (input_byte >= "0" && input_byte <= "9") begin
+                        command_data.address = command_data.address << 4;
+                        command_data.address[$clog2(`RAM_LINE_WORDS)+:4] = input_byte - "0";
+                    end else if (input_byte >= "a" && input_byte <= "f") begin
+                        command_data.address = command_data.address << 4;
+                        command_data.address[$clog2(`RAM_LINE_WORDS)+:4] = input_byte - "a" + 10;
+                    end else if (input_byte >= "A" && input_byte <= "F") begin
+                        command_data.address = command_data.address << 4;
+                        command_data.address[$clog2(`RAM_LINE_WORDS)+:4] = input_byte - "A" + 10;
+                    end else if (input_byte == "?") begin
+                        command_valid = 1;
+                        command_data.write = 0;
+                        command_data.data = 0;
+                    end else if (input_byte == "=") begin
+                        command_data.write = 1;
+                        command_data.data = 0;
+                        state = READ_DATA;
+                    end else begin
+                        command_data.address = 0;
+                        command_data.write = 0;
+                        command_data.data = 0;
+                    end
+                end
+
+                READ_DATA: begin
+                    automatic bit [$bits(command_data.data)-1:0] flat_data = command_data.data;
+                    flat_data = flat_data << 4;
+                    if (input_byte >= "0" && input_byte <= "9") begin
+                        flat_data[3:0] = input_byte - "0";
+                        command_data.data = flat_data;
+                    end else if (input_byte >= "a" && input_byte <= "f") begin
+                        flat_data[3:0] = input_byte - "a" + 10;
+                        command_data.data = flat_data;
+                    end else if (input_byte >= "A" && input_byte <= "F") begin
+                        flat_data[3:0] = input_byte - "A" + 10;
+                        command_data.data = flat_data;
+                    end else begin
+                        command_valid = 1;
+                        state = state.first;
+                    end
+                end
+
+                endcase
+                input_byte_valid = 0;
+            end
+
+            uart_ready = !echo_valid && !input_byte_valid;
+        end
+    end
+
+endmodule
-- 
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