1 files changed, 90 insertions, 23 deletions

diff --git a/hdl/command_parser.sv b/hdl/command_parser.sv
index 5c49db9..cf4fe65 100644
--- a/hdl/command_parser.sv
+++ b/hdl/command_parser.sv
@@ -21,29 +21,32 @@ module command_parser
     bit         input_byte_valid;
     uart_byte_t input_byte;
 
+    bit [`RAM_ADDRESS_BITS:0]   zero_count;
+
     (* syn_encoding = "one-hot" *) enum int unsigned
-        {   READ_ADDRESS_OR_COMMAND
+        {   READ_COMMAND
+        ,   READ_ADDRESS
         ,   READ_DATA
+        ,   READ_ZERO_COUNT
+        ,   ZERO_MEMORY
         } state;
 
     always @(posedge clock) begin
         if (reset) begin
             uart_ready = 0;
             command_valid = 0;
+            for (int i = 0; i < `RAM_LINE_WORDS; i = i + 1)
+                command_data.mask[i] = ~0;
+            command_data.tag = TAG;
             input_byte_valid = 0;
             input_byte = 0;
+            zero_count = 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;
+                ++command_data.address;
             end
             if (uart_ready && uart_valid) begin
                 echo_valid = 1;
@@ -52,10 +55,42 @@ module command_parser
                 input_byte = uart_data;
             end
 
-            if (!command_valid && input_byte_valid) begin
+            if (!command_valid) begin
                 case (state)
 
-                READ_ADDRESS_OR_COMMAND: begin
+                READ_COMMAND: if (input_byte_valid) begin
+                    case (input_byte)
+
+                    "@": begin
+                        command_data.address = 0;
+                        state = READ_ADDRESS;
+                    end
+
+                    "?": begin
+                        command_valid = 1;
+                        command_data.write = 0;
+                    end
+
+                    "=": begin
+                        command_data.write = 1;
+                        for (int i = 0; i < `RAM_LINE_WORDS; i = i + 1)
+                            command_data.data[i] = 0;
+                        state = READ_DATA;
+                    end
+
+                    "!": begin
+                        command_data.write = 1;
+                        for (int i = 0; i < `RAM_LINE_WORDS; i = i + 1)
+                            command_data.data[i] = 0;
+                        zero_count = 0;
+                        state = READ_ZERO_COUNT;
+                    end
+
+                    endcase
+                    input_byte_valid = 0;
+                end
+
+                READ_ADDRESS: if (input_byte_valid) begin
                     if (input_byte >= "0" && input_byte <= "9") begin
                         command_data.address = command_data.address << 4;
                         command_data.address[$clog2(`RAM_LINE_WORDS)+:4] = input_byte - "0";
@@ -65,22 +100,13 @@ module command_parser
                     end else if (input_byte >= "A" && input_byte <= "F") begin
                         command_data.address = command_data.address << 4;
                         command_data.address[$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;
+                        state = state.first;
                     end
+                    input_byte_valid = 0;
                 end
 
-                READ_DATA: begin
+                READ_DATA: if (input_byte_valid) 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
@@ -96,10 +122,51 @@ module command_parser
                         command_valid = 1;
                         state = state.first;
                     end
+                    input_byte_valid = 0;
+                end
+
+                READ_ZERO_COUNT: if (input_byte_valid) begin
+                    if (input_byte >= "0" && input_byte <= "9") begin
+                        zero_count = zero_count << 4;
+                        zero_count[3:0] = input_byte - "0";
+                    end else if (input_byte >= "a" && input_byte <= "f") begin
+                        zero_count = zero_count << 4;
+                        zero_count[3:0] = input_byte - "a" + 10;
+                    end else if (input_byte >= "A" && input_byte <= "F") begin
+                        zero_count = zero_count << 4;
+                        zero_count[3:0] = input_byte - "A" + 10;
+                    end else begin
+                        state = ZERO_MEMORY;
+                    end
+                    input_byte_valid = 0;
+                end
+
+`ifdef SLOW_ZEROING
+                ZERO_MEMORY: if (!echo_valid) begin
+                    if (zero_count == 0) begin
+                        echo_valid = 1;
+                        echo_data = "\n";
+                        state = state.first;
+                    end else begin
+                        echo_valid = 1;
+                        echo_data = ".";
+                        command_valid = 1;
+                        --zero_count;
+                    end
+                end
+`else
+                ZERO_MEMORY: begin
+                    if (zero_count == 0) begin
+                        state = state.first;
+                    end else begin
+                        command_valid = 1;
+                        if (--zero_count == 0)
+                            state = state.first;
+                    end
                 end
+`endif
 
                 endcase
-                input_byte_valid = 0;
             end
 
             uart_ready = !echo_valid && !input_byte_valid;