From cfcf94a8757a0ac4e701342045f1879dcb44e5dd Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Mon, 14 Mar 2022 10:45:45 -0500
Subject: [PATCH] Integrate uart controller into top level module

Adds new chip select for the UART, and a new entry in the data_out mux
for the UART.
---
 hw/fpga/addr_decode.sv |  4 +++-
 hw/fpga/super6502.sv   | 11 ++++++++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/hw/fpga/addr_decode.sv b/hw/fpga/addr_decode.sv
index 1b4dd5e..83f3c57 100644
--- a/hw/fpga/addr_decode.sv
+++ b/hw/fpga/addr_decode.sv
@@ -2,11 +2,13 @@ module addr_decode(
     input logic [15:0] addr,
     output logic ram_cs,
     output logic rom_cs,
-    output logic hex_cs
+    output logic hex_cs,
+    output logic uart_cs
 );
 
 assign rom_cs = addr[15];
 assign ram_cs = ~addr[15] && addr < 16'h7ff0;
 assign hex_cs = addr >= 16'h7ff0 && addr < 16'h7ff4;
+assign uart_cs = addr >= 16'h7ff4 && addr < 16'h7ff6;
 
 endmodule
diff --git a/hw/fpga/super6502.sv b/hw/fpga/super6502.sv
index 1411643..54bcf61 100644
--- a/hw/fpga/super6502.sv
+++ b/hw/fpga/super6502.sv
@@ -40,10 +40,12 @@ assign cpu_data = cpu_rwb ? cpu_data_out : 'z;
 
 logic [7:0] rom_data_out;
 logic [7:0] ram_data_out;
+logic [7:0] uart_data_out;
 
 logic ram_cs;
 logic rom_cs;
 logic hex_cs;
+logic uart_cs;
 
 cpu_clk cpu_clk(
 	.inclk0(clk_50),
@@ -65,7 +67,8 @@ addr_decode decode(
     .addr(cpu_addr),
     .ram_cs(ram_cs),
     .rom_cs(rom_cs),
-    .hex_cs(hex_cs)
+    .hex_cs(hex_cs),
+    .uart_cs(uart_cs)
 );
 
 
@@ -74,6 +77,8 @@ always_comb begin
         cpu_data_out = ram_data_out;
     else if (rom_cs)
         cpu_data_out = rom_data_out;
+    else if (uart_cs)
+        cpu_data_out = uart_data_out;
     else
         cpu_data_out = 'x;
 end
@@ -112,11 +117,11 @@ uart uart(
     .rst(rst),
     .rw(cpu_rwb),
     .data_in(cpu_data_in),
-    .cs(),
+    .cs(uart_cs),
     .addr(cpu_addr[1:0]),
     .RXD(UART_RXD),
     .TXD(UART_TXD),
-    .data_out()
+    .data_out(uart_data_out)
 );
  
 endmodule