remove sim submodule

.gitmodules

@@ -1,6 +1,3 @@
 [submodule "sw/cc65"]
 	path = sw/cc65
 	url = https://git.byronlathi.com/bslathi19/cc65
-[submodule "hw/efinix_fpga/simulation/verilog-6502"]
-	path = hw/efinix_fpga/simulation/verilog-6502
-	url = https://git.byronlathi.com/bslathi19/verilog-6502

hw/efinix_fpga/simulation/src/verilog-6502/ALU.v

@@ -1,108 +0,0 @@
-/*
- * ALU.
- *
- * AI and BI are 8 bit inputs. Result in OUT.
- * CI is Carry In.
- * CO is Carry Out.
- *
- * op[3:0] is defined as follows:
- *
- * 0011   AI + BI
- * 0111   AI - BI
- * 1011   AI + AI
- * 1100   AI | BI
- * 1101   AI & BI
- * 1110   AI ^ BI
- * 1111   AI
- *
- */
-
-module ALU( clk, op, right, AI, BI, CI, CO, BCD, OUT, V, Z, N, HC, RDY );
-	input clk;
-	input right;
-	input [3:0] op;		// operation
-	input [7:0] AI;
-	input [7:0] BI;
-	input CI;
-	input BCD;		// BCD style carry
-	output [7:0] OUT;
-	output CO;
-	output V;
-	output Z;
-	output N;
-	output HC;
-	input RDY;
-
-reg [7:0] OUT;
-reg CO;
-wire V;
-wire Z;
-reg N;
-reg HC;
-
-reg AI7;
-reg BI7;
-reg [8:0] temp_logic;
-reg [7:0] temp_BI;
-reg [4:0] temp_l;
-reg [4:0] temp_h;
-wire [8:0] temp = { temp_h, temp_l[3:0] };
-wire adder_CI = (right | (op[3:2] == 2'b11)) ? 0 : CI;
-
-// calculate the logic operations. The 'case' can be done in 1 LUT per
-// bit. The 'right' shift is a simple mux that can be implemented by
-// F5MUX.
-always @*  begin
-	case( op[1:0] )
-	    2'b00: temp_logic = AI | BI;
-	    2'b01: temp_logic = AI & BI;
-	    2'b10: temp_logic = AI ^ BI;
-	    2'b11: temp_logic = AI;
-	endcase
-
-	if( right )
-	    temp_logic = { AI[0], CI, AI[7:1] };
-end
-
-// Add logic result to BI input. This only makes sense when logic = AI.
-// This stage can be done in 1 LUT per bit, using carry chain logic.
-always @* begin
-	case( op[3:2] )
-	    2'b00: temp_BI = BI;	// A+B
-	    2'b01: temp_BI = ~BI;	// A-B
-	    2'b10: temp_BI = temp_logic;	// A+A
-	    2'b11: temp_BI = 0;		// A+0
-	endcase	
-end
-
-// HC9 is the half carry bit when doing BCD add
-wire HC9 = BCD & (temp_l[3:1] >= 3'd5);
-
-// CO9 is the carry-out bit when doing BCD add
-wire CO9 = BCD & (temp_h[3:1] >= 3'd5);
-
-// combined half carry bit
-wire temp_HC = temp_l[4] | HC9;
-
-// perform the addition as 2 separate nibble, so we get
-// access to the half carry flag
-always @* begin
-	temp_l = temp_logic[3:0] + temp_BI[3:0] + adder_CI;
-	temp_h = temp_logic[8:4] + temp_BI[7:4] + temp_HC;
-end
-
-// calculate the flags 
-always @(posedge clk)
-    if( RDY ) begin
-	AI7 <= AI[7];
-	BI7 <= temp_BI[7];
-	OUT <= temp[7:0];
-	CO  <= temp[8] | CO9;
-	N   <= temp[7];
-	HC  <= temp_HC;
-    end
-
-assign V = AI7 ^ BI7 ^ CO ^ N;
-assign Z = ~|OUT;
-
-endmodule

hw/efinix_fpga/simulation/src/verilog-6502/README.md

@@ -1,69 +0,0 @@
-========================================================
-A Verilog HDL version of the old MOS 6502 and 65C02 CPUs
-========================================================
-
-Original 6502 core by Arlet Ottens
-
-65C02 extensions by David Banks and Ed Spittles
-
-==========
-6502 Core
-==========
-
-Arlet's original 6502 core (cpu.v) is unchanged.
-
-Note: the 6502/65C02 cores assumes a synchronous memory. This means
-that valid data (DI) is expected on the cycle *after* valid
-address. This allows direct connection to (Xilinx) block RAMs. When
-using asynchronous memory, I suggest registering the address/control
-lines for glitchless output signals.
-
-[Also check out my new 65C02 project](https://github.com/Arlet/verilog-65c02)
-
-Have fun. 
-
-==========
-65C02 Core
-==========
-
-A second core (cpu_65c02.v) has been added, based on Arlet's 6502
-core, with additional 65C02 instructions and addressing modes:
-- PHX, PHY, PLX, PLY
-- BRA
-- INC A, DEC A
-- (zp) addressing mode
-- STZ
-- BIT zpx, absx, imm
-- TSB/TRB
-- JMP (,X)
-- NOPs (optional)
-- 65C02 BCD N/Z flags (optional, disabled)
-
-The Rockwell/WDC specific instructions (RMB/SMB/BBR/BBS/WAI/STP) are
-not currently implemented
-
-The 65C02 core passes the Dormann 6502 test suite, and also passes the
-Dormann 65C02 test suite if the optional support for NOPs and 65C02
-BCD flags is enabled.
-
-It has been tested as a BBC Micro "Matchbox" 65C02 Co Processor, in a
-XC6SLX9-2 FPGA, running at 80MHz using 64KB of internel block RAM. It
-just meets timing at 80MHz in this environment. It successfully runs
-BBC Basic IV and Tube Elite.
-
-============
-Known Issues
-============
-
-The Matchbox Co Processor needed one wait state (via RDY) to be added
-to each ROM access (only needed early in the boot process, as
-eventually everything runs from RAM). The DIHOLD logic did not work
-correctly with a single wait state, and so has been commented out.
-
-I now believe the correct fix is actually just:
-
-always @(posedge clk )
-    if( RDY )
-        DIHOLD <= DI;
- 
-assign DIMUX = ~RDY ? DIHOLD : DI;