b2344d986e
Currently an interrupt is triggered any time there is any activity on the UART_RXD line, but later it will only trigger once there is data ready to be read.
152 lines
2.8 KiB
Systemverilog
152 lines
2.8 KiB
Systemverilog
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module super6502(
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input clk_50,
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input logic rst_n,
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input logic button_1,
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input logic [15:0] cpu_addr,
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inout logic [7:0] cpu_data,
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input logic cpu_vpb,
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input logic cpu_mlb,
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input logic cpu_rwb,
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input logic cpu_sync,
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output logic cpu_led,
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output logic cpu_resb,
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output logic cpu_rdy,
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output logic cpu_sob,
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output logic cpu_irqb,
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output logic cpu_phi2,
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output logic cpu_be,
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output logic cpu_nmib,
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output logic [6:0] HEX0, HEX1, HEX2, HEX3, HEX4, HEX5,
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input logic UART_RXD,
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output logic UART_TXD
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);
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logic rst;
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assign rst = ~rst_n;
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logic clk;
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logic [7:0] cpu_data_in;
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assign cpu_data_in = cpu_data;
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logic [7:0] cpu_data_out;
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assign cpu_data = cpu_rwb ? cpu_data_out : 'z;
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logic [7:0] rom_data_out;
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logic [7:0] ram_data_out;
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logic [7:0] uart_data_out;
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logic [7:0] irq_data_out;
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logic ram_cs;
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logic rom_cs;
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logic hex_cs;
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logic uart_cs;
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logic irq_cs;
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cpu_clk cpu_clk(
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.inclk0(clk_50),
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.c0(clk)
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);
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always @(posedge clk) begin
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cpu_phi2 <= ~cpu_phi2;
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end
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assign cpu_rdy = '1;
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assign cpu_sob = '0;
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assign cpu_resb = rst_n;
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assign cpu_be = '1;
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assign cpu_nmib = '1;
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assign cpu_irqb = irq_data_out == 0;
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addr_decode decode(
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.addr(cpu_addr),
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.ram_cs(ram_cs),
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.rom_cs(rom_cs),
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.hex_cs(hex_cs),
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.uart_cs(uart_cs),
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.irq_cs(irq_cs)
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);
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always_comb begin
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if (ram_cs)
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cpu_data_out = ram_data_out;
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else if (rom_cs)
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cpu_data_out = rom_data_out;
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else if (uart_cs)
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cpu_data_out = uart_data_out;
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else if (irq_cs)
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cpu_data_out = irq_data_out;
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else
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cpu_data_out = 'x;
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end
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ram main_memory(
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.address(cpu_addr[14:0]),
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.clock(clk),
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.data(cpu_data_in),
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.wren(~cpu_rwb & ram_cs),
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.q(ram_data_out)
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);
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rom boot_rom(
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.address(cpu_addr[14:0]),
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.clock(clk),
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.q(rom_data_out)
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);
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SevenSeg segs(
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.clk(clk),
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.rst(rst),
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.rw(cpu_rwb),
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.data(cpu_data_in),
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.cs(hex_cs),
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.addr(cpu_addr[1:0]),
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.HEX0(HEX0), .HEX1(HEX1), .HEX2(HEX2), .HEX3(HEX3), .HEX4(HEX4), .HEX5(HEX5)
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);
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logic uart_irq;
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uart uart(
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.clk_50(clk_50),
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.clk(clk),
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.rst(rst),
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.rw(cpu_rwb),
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.data_in(cpu_data_in),
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.cs(uart_cs),
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.addr(cpu_addr[1:0]),
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.RXD(UART_RXD),
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.TXD(UART_TXD),
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.irq(uart_irq),
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.data_out(uart_data_out)
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);
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always_ff @(posedge clk_50) begin
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if (rst)
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irq_data_out <= '0;
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else if (irq_cs && ~cpu_rwb)
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irq_data_out <= irq_data_out & cpu_data_in;
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else begin
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if (~button_1)
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irq_data_out[0] <= '1;
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if (uart_irq)
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irq_data_out[1] <= '1;
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end
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end
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endmodule
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