Add chip selects to rom/ram

Slightly easier to work with ppu and cart memory spaces this way

rtl/gb.sv

@@ -26,11 +26,9 @@ logic        rom_sel;
 logic [ 7:0] rom_rdata;
 
 logic        hiram_sel;
-logic        hiram_we;
 logic [ 7:0] hiram_rdata;
 
 logic        vram_sel;
-logic        vram_we;
 logic [ 7:0] vram_rdata;
 
 cpu cpu_inst (
@@ -50,8 +48,7 @@ ppu ppu_inst (
   .cpu_addr_i (cpu_addr),
   .cpu_rdata_o(cpu_ppu_rdata),
   .cpu_we_i   (cpu_we),
-  .cpu_wdata_i(cpu_wdata),
-  .cpu_addr_sel_o(ppu_sel)
+  .cpu_wdata_i(cpu_wdata)
 );
 
 assign rom_enable_r = '1;
@@ -60,13 +57,10 @@ assign rom_sel   = rom_enable_r & ~(|cpu_addr[15:8]);
 assign vram_sel  = (cpu_addr[15:13] == 3'b100);
 assign hiram_sel = (&cpu_addr[15:7]) & ~(&cpu_addr[6:0]);
 
-assign vram_we  = vram_sel  & cpu_we;
-assign hiram_we = hiram_sel & cpu_we;
-
-assign cpu_rdata = ({8{  rom_sel}} & rom_rdata)  |
-                   ({8{ vram_sel}} & vram_rdata) |
-                   ({8{hiram_sel}} & hiram_rdata)|
-                   ({8{  ppu_sel}} & cpu_ppu_rdata);
+assign cpu_rdata = rom_rdata     |
+                   vram_rdata    |
+                   hiram_rdata   |
+                   cpu_ppu_rdata;
 
 rom #(
   .FILE_NAME("DMG_ROM.bin"),
@@ -74,6 +68,8 @@ rom #(
   .DATA_W   (8)
 ) rom_inst (
   .clk      (clk),
+  .nreset   (nreset),
+  .cs_i     (rom_sel),
   .address_i(cpu_addr[7:0]),
   .rdata_o  (rom_rdata)
 );
@@ -83,9 +79,11 @@ ram #(
   .DATA_W   (8)
 ) vram_inst (
   .clk       (clk),
+  .nreset    (nreset),
+  .cs_i      (vram_sel),
   .address_i (cpu_addr[12:0]),
   .rdata_o   (vram_rdata),
-  .we_i      (vram_we),
+  .we_i      (cpu_we),
   .wdata_i   (cpu_wdata)
 );
 
@@ -94,9 +92,11 @@ ram #(
   .DATA_W (8)
 ) hiram_inst (
   .clk       (clk),
+  .nreset    (nreset),
+  .cs_i      (hiram_sel),
   .address_i (cpu_addr[6:0]),
   .rdata_o   (hiram_rdata),
-  .we_i      (hiram_we),
+  .we_i      (cpu_we),
   .wdata_i   (cpu_wdata)
 );