From 92420e248d4449a2aa61e92f05c0867912d48d56 Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Wed, 16 Feb 2022 14:44:01 -0800
Subject: Split into multiple files.

---
 hdl/command_parser.sv | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 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..d6775ad
--- /dev/null
+++ b/hdl/command_parser.sv
@@ -0,0 +1,102 @@
+module command_parser
+    (   input   bit         clock
+    ,   input   bit         resetn
+
+    ,   output  bit         uart_ready
+    ,   input   bit         uart_valid
+    ,   input   bit [7:0]   uart_data
+
+    ,   input   bit         echo_ready
+    ,   output  bit         echo_valid
+    ,   output  bit [7:0]   echo_data
+
+    ,   input   bit         command_ready
+    ,   output  bit         command_valid
+    ,   output  bit [23:0]  command_address
+    ,   output  bit         command_write
+    ,   output  bit [15:0]  command_data
+    );
+
+    bit         input_byte_valid;
+    bit [7:0]   input_byte;
+
+    enum
+        {   READ_ADDRESS_OR_COMMAND
+        ,   READ_DATA_1
+        ,   READ_DATA_2
+        ,   READ_DATA_3
+        ,   READ_DATA_4
+        } state;
+
+    always @(posedge clock) begin
+        if (!resetn) begin
+            uart_ready = 0;
+            command_valid = 0;
+            command_address = 0;
+            command_write = 0;
+            command_data = 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 = 0;
+            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_address = command_address << 4;
+                        command_address[3:0] = input_byte - "0";
+                    end else if (input_byte >= "a" && input_byte <= "f") begin
+                        command_address = command_address << 4;
+                        command_address[3:0] = input_byte - "a" + 10;
+                    end else if (input_byte >= "A" && input_byte <= "F") begin
+                        command_address = command_address << 4;
+                        command_address[3:0] = input_byte - "A" + 10;
+                    end else if (input_byte == "?") begin
+                        command_valid = 1;
+                        command_write = 0;
+                        command_data = 0;
+                    end else if (input_byte == "=") begin
+                        command_write = 1;
+                        command_data = 0;
+                        state = READ_DATA_1;
+                    end
+                end
+
+                READ_DATA_1, READ_DATA_2, READ_DATA_3, READ_DATA_4: begin
+                    if (input_byte >= "0" && input_byte <= "9") begin
+                        command_data = command_data << 4;
+                        command_data[3:0] = input_byte - "0";
+                        state = state.next;
+                    end else if (input_byte >= "a" && input_byte <= "f") begin
+                        command_data = command_data << 4;
+                        command_data[3:0] = input_byte - "a" + 10;
+                        state = state.next;
+                    end else if (input_byte >= "A" && input_byte <= "F") begin
+                        command_data = command_data << 4;
+                        command_data[3:0] = input_byte - "A" + 10;
+                        state = state.next;
+                    end else begin
+                        state = state.first;
+                    end
+                    command_valid = state == state.first;
+                end
+
+                endcase
+                input_byte_valid = 0;
+            end
+
+            uart_ready = !echo_valid && !input_byte_valid;
+        end
+    end
+
+endmodule
-- 
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