From 71f08bdf159e8c89ab0a047b4091346719417ed4 Mon Sep 17 00:00:00 2001
From: Waylon Cude <waylon.cude@finzdani.net>
Date: Fri, 6 Jun 2025 18:13:14 -0700
Subject: [PATCH] Add CRC generation for sd card

Works great according to the testbench
---
 SDVD.xpr                                      | 57 ++++++++++++++++-
 design/sd/crc_gen.sv                          | 41 ++++++++++++
 design/sd/send_command.sv                     | 14 +++++
 verification/sd/crc_gen_tb.sv                 | 49 +++++++++++++++
 .../waveform_configs/crc_gen_tb_behav.wcfg    | 63 +++++++++++++++++++
 5 files changed, 222 insertions(+), 2 deletions(-)
 create mode 100644 design/sd/crc_gen.sv
 create mode 100644 design/sd/send_command.sv
 create mode 100644 verification/sd/crc_gen_tb.sv
 create mode 100644 verification/waveform_configs/crc_gen_tb_behav.wcfg

diff --git a/SDVD.xpr b/SDVD.xpr
index f7a85cb..32d1240 100644
--- a/SDVD.xpr
+++ b/SDVD.xpr
@@ -45,7 +45,7 @@
     <Option Name="SimulatorGccVersionActiveHdl" Val="9.3.0"/>
     <Option Name="BoardPart" Val=""/>
     <Option Name="SourceMgmtMode" Val="DisplayOnly"/>
-    <Option Name="ActiveSimSet" Val="rom_sd_tb"/>
+    <Option Name="ActiveSimSet" Val="crc_gen_tb"/>
     <Option Name="DefaultLib" Val="xil_defaultlib"/>
     <Option Name="ProjectType" Val="Default"/>
     <Option Name="IPRepoPath" Val="$PPRDIR/../../../fpga/vivado-library"/>
@@ -61,7 +61,7 @@
     <Option Name="IPStaticSourceDir" Val="$PIPUSERFILESDIR/ipstatic"/>
     <Option Name="EnableBDX" Val="FALSE"/>
     <Option Name="DSABoardId" Val="nexys-a7-100t"/>
-    <Option Name="WTXSimLaunchSim" Val="133"/>
+    <Option Name="WTXSimLaunchSim" Val="138"/>
     <Option Name="WTModelSimLaunchSim" Val="0"/>
     <Option Name="WTQuestaLaunchSim" Val="0"/>
     <Option Name="WTIesLaunchSim" Val="0"/>
@@ -202,6 +202,20 @@
           <Attr Name="UsedIn" Val="simulation"/>
         </FileInfo>
       </File>
+      <File Path="$PPRDIR/design/sd/send_command.sv">
+        <FileInfo>
+          <Attr Name="UsedIn" Val="synthesis"/>
+          <Attr Name="UsedIn" Val="implementation"/>
+          <Attr Name="UsedIn" Val="simulation"/>
+        </FileInfo>
+      </File>
+      <File Path="$PPRDIR/design/sd/crc_gen.sv">
+        <FileInfo>
+          <Attr Name="UsedIn" Val="synthesis"/>
+          <Attr Name="UsedIn" Val="implementation"/>
+          <Attr Name="UsedIn" Val="simulation"/>
+        </FileInfo>
+      </File>
       <Config>
         <Option Name="DesignMode" Val="RTL"/>
         <Option Name="TopModule" Val="nexys_a7_top"/>
@@ -430,6 +444,45 @@
         <Option Name="xsim.simulate.runtime" Val="1s"/>
       </Config>
     </FileSet>
+    <FileSet Name="crc_gen_tb" Type="SimulationSrcs" RelSrcDir="$PSRCDIR/crc_gen_tb" RelGenDir="$PGENDIR/crc_gen_tb">
+      <File Path="$PPRDIR/verification/sd/rom_sd_tb.sv">
+        <FileInfo>
+          <Attr Name="UsedIn" Val="synthesis"/>
+          <Attr Name="UsedIn" Val="implementation"/>
+          <Attr Name="UsedIn" Val="simulation"/>
+        </FileInfo>
+      </File>
+      <File Path="$PPRDIR/verification/sd/crc_gen_tb.sv">
+        <FileInfo>
+          <Attr Name="UsedIn" Val="synthesis"/>
+          <Attr Name="UsedIn" Val="implementation"/>
+          <Attr Name="UsedIn" Val="simulation"/>
+        </FileInfo>
+      </File>
+      <File Path="$PPRDIR/verification/waveform_configs/crc_gen_tb_behav.wcfg">
+        <FileInfo>
+          <Attr Name="UsedIn" Val="simulation"/>
+        </FileInfo>
+      </File>
+      <Config>
+        <Option Name="DesignMode" Val="RTL"/>
+        <Option Name="TopModule" Val="crc_gen_tb"/>
+        <Option Name="TopLib" Val="xil_defaultlib"/>
+        <Option Name="TransportPathDelay" Val="0"/>
+        <Option Name="TransportIntDelay" Val="0"/>
+        <Option Name="SelectedSimModel" Val="rtl"/>
+        <Option Name="PamDesignTestbench" Val=""/>
+        <Option Name="PamDutBypassFile" Val="xil_dut_bypass"/>
+        <Option Name="PamSignalDriverFile" Val="xil_bypass_driver"/>
+        <Option Name="PamPseudoTop" Val="pseudo_tb"/>
+        <Option Name="SrcSet" Val="sources_1"/>
+        <Option Name="XSimWcfgFile" Val="$PPRDIR/verification/waveform_configs/crc_gen_tb_behav.wcfg"/>
+        <Option Name="CosimPdi" Val=""/>
+        <Option Name="CosimPlatform" Val=""/>
+        <Option Name="CosimElf" Val=""/>
+        <Option Name="xsim.simulate.runtime" Val="1s"/>
+      </Config>
+    </FileSet>
   </FileSets>
   <Simulators>
     <Simulator Name="XSim">
diff --git a/design/sd/crc_gen.sv b/design/sd/crc_gen.sv
new file mode 100644
index 0000000..4a16aef
--- /dev/null
+++ b/design/sd/crc_gen.sv
@@ -0,0 +1,41 @@
+// parameterizable sequential crc generator
+// This probably could be combinational logic too, though it would be way slow
+module crc_gen #(
+    parameter CRCBITS=7,
+    parameter COMMANDLEN=40,
+    parameter POLYNOMIAL='h89
+) (
+    input clk,
+    input reset,
+    input start,
+    input [COMMANDLEN-1:0] num,
+    output logic ready,
+    output logic [CRCBITS-1:0] crc
+);
+
+logic [$clog2(COMMANDLEN):0] counter;
+logic [COMMANDLEN+CRCBITS-1:0] div_reg;
+
+always_ff @(posedge clk) begin
+    if (reset) begin
+        counter <= 0;
+        crc <= 0;
+    end
+    else if (start) begin
+        counter <= COMMANDLEN;
+        div_reg <= {num, {CRCBITS{1'b0}}};
+        ready <= 0;
+    end
+    else if (counter != 0) begin
+        if (div_reg[counter+CRCBITS-1] == 1) begin
+            div_reg <= div_reg ^ (POLYNOMIAL << (counter-1));
+        end
+        counter <= counter - 1;
+    end
+    else begin
+        ready <= 1;
+        crc <= div_reg[CRCBITS-1:0];
+    end
+end
+
+endmodule
diff --git a/design/sd/send_command.sv b/design/sd/send_command.sv
new file mode 100644
index 0000000..1477512
--- /dev/null
+++ b/design/sd/send_command.sv
@@ -0,0 +1,14 @@
+module send_command(
+    input clk, 
+    input reset,
+    input start,
+    input [5:0] command,
+    input [31:0] arguments
+);
+
+
+// Some commands have hardcoded crcs, and as such they can be found in a LUT,
+// otherwise we need to shell out to the crc module and wait a while for it to
+// run
+
+endmodule
diff --git a/verification/sd/crc_gen_tb.sv b/verification/sd/crc_gen_tb.sv
new file mode 100644
index 0000000..062c97a
--- /dev/null
+++ b/verification/sd/crc_gen_tb.sv
@@ -0,0 +1,49 @@
+module crc_gen_tb;
+    parameter CRCBITS=7;
+    parameter COMMANDLEN=40;
+    parameter POLYNOMIAL='h89;
+
+    logic clk, reset, start, ready;
+    logic [COMMANDLEN-1:0] num;
+    logic [CRCBITS-1:0] crc;
+
+    logic [CRCBITS-1:0] test_cases [logic [COMMANDLEN-1:0]];
+
+    crc_gen #(CRCBITS,COMMANDLEN,POLYNOMIAL) dut (.*);
+
+    initial begin
+        clk = 0;
+        forever #10 clk = ~clk;
+    end
+
+    initial begin
+        test_cases = '{
+            'h1234567890: 'h10,
+            'hBEEFB05535: 'h05,
+            'h5544992211: 'h17,
+            '0: '0
+        };
+
+        reset = 1;
+        start = 0;
+        repeat (2) @(posedge clk);
+        reset = 0;
+        @(posedge clk);
+        foreach (test_cases[key]) begin
+            wait (ready);
+            num = key;
+            @(posedge clk);
+            start = 1;
+            @(posedge clk);
+            start = 0;
+            @(posedge clk);
+            wait(ready);
+            assert (crc === test_cases[key])
+                else $error("Invalid crc, found 0x%x but expected 0x%x",crc,test_cases[key]);
+        end
+
+        $finish;
+
+    end
+
+endmodule
diff --git a/verification/waveform_configs/crc_gen_tb_behav.wcfg b/verification/waveform_configs/crc_gen_tb_behav.wcfg
new file mode 100644
index 0000000..36b9a84
--- /dev/null
+++ b/verification/waveform_configs/crc_gen_tb_behav.wcfg
@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<wave_config>
+   <wave_state>
+   </wave_state>
+   <db_ref_list>
+      <db_ref path="crc_gen_tb_behav.wdb" id="1">
+         <top_modules>
+            <top_module name="crc_gen_tb" />
+            <top_module name="glbl" />
+         </top_modules>
+      </db_ref>
+   </db_ref_list>
+   <zoom_setting>
+      <ZoomStartTime time="609.789 ns"></ZoomStartTime>
+      <ZoomEndTime time="1,276.290 ns"></ZoomEndTime>
+      <Cursor1Time time="209.703 ns"></Cursor1Time>
+   </zoom_setting>
+   <column_width_setting>
+      <NameColumnWidth column_width="533"></NameColumnWidth>
+      <ValueColumnWidth column_width="219"></ValueColumnWidth>
+   </column_width_setting>
+   <WVObjectSize size="10" />
+   <wvobject type="logic" fp_name="/crc_gen_tb/clk">
+      <obj_property name="ElementShortName">clk</obj_property>
+      <obj_property name="ObjectShortName">clk</obj_property>
+   </wvobject>
+   <wvobject type="logic" fp_name="/crc_gen_tb/reset">
+      <obj_property name="ElementShortName">reset</obj_property>
+      <obj_property name="ObjectShortName">reset</obj_property>
+   </wvobject>
+   <wvobject type="logic" fp_name="/crc_gen_tb/start">
+      <obj_property name="ElementShortName">start</obj_property>
+      <obj_property name="ObjectShortName">start</obj_property>
+   </wvobject>
+   <wvobject type="logic" fp_name="/crc_gen_tb/ready">
+      <obj_property name="ElementShortName">ready</obj_property>
+      <obj_property name="ObjectShortName">ready</obj_property>
+   </wvobject>
+   <wvobject type="array" fp_name="/crc_gen_tb/num">
+      <obj_property name="ElementShortName">num[39:0]</obj_property>
+      <obj_property name="ObjectShortName">num[39:0]</obj_property>
+   </wvobject>
+   <wvobject type="array" fp_name="/crc_gen_tb/crc">
+      <obj_property name="ElementShortName">crc[6:0]</obj_property>
+      <obj_property name="ObjectShortName">crc[6:0]</obj_property>
+   </wvobject>
+   <wvobject type="array" fp_name="/crc_gen_tb/CRCBITS">
+      <obj_property name="ElementShortName">CRCBITS[31:0]</obj_property>
+      <obj_property name="ObjectShortName">CRCBITS[31:0]</obj_property>
+   </wvobject>
+   <wvobject type="array" fp_name="/crc_gen_tb/COMMANDLEN">
+      <obj_property name="ElementShortName">COMMANDLEN[31:0]</obj_property>
+      <obj_property name="ObjectShortName">COMMANDLEN[31:0]</obj_property>
+   </wvobject>
+   <wvobject type="array" fp_name="/crc_gen_tb/POLYNOMIAL">
+      <obj_property name="ElementShortName">POLYNOMIAL[31:0]</obj_property>
+      <obj_property name="ObjectShortName">POLYNOMIAL[31:0]</obj_property>
+   </wvobject>
+   <wvobject type="array" fp_name="/crc_gen_tb/dut/counter">
+      <obj_property name="ElementShortName">counter[6:0]</obj_property>
+      <obj_property name="ObjectShortName">counter[6:0]</obj_property>
+   </wvobject>
+</wave_config>