Add chip enable correctness for CellularRAM.

[firearm.git] / Terminal.v

module Terminal(
	input clk,
	
	input cp_req,
	input [31:0] cp_insn,
	output reg cp_ack,
	output reg cp_busy,
	input cp_rnw,
	output reg [31:0] cp_read = 0,
	input [31:0] cp_write
`ifdef verilator
`else
	, output reg [8:0] sys_odata = 0,
	input [8:0] sys_idata,
	output reg sys_tookdata = 0
`endif
);
	
	/* Terminal pretends to be cp5. */
	reg towrite = 0;
	reg [7:0] data = 0;
	reg [8:0] indata = 0;	/* High bit is if data is present. */
	reg didread = 0;
	
	always @(*)
	begin
		towrite = 0;
		data = 8'hxx;
		cp_ack = 0;
		cp_busy = 0;
		cp_read = 0;
		didread = 0;
		if (cp_req && (cp_rnw == 0) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0000) && (cp_insn[11:8] == 4'h5))
		begin
			towrite = 1;
			data = cp_write[7:0];
			cp_ack = 1;
		end else if (cp_req && (cp_rnw == 1) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0001) && (cp_insn[11:8] == 4'h5))
		begin
			cp_read = {23'h0, indata[8:0]};
			cp_ack = 1;
			didread = cp_insn[7:5] == 1;
		end
	end
`ifdef verilator	
	always @(posedge clk)
		if (towrite)
			$c("{extern void term_output(unsigned char d); term_output(",data,");}");
		else if (didread || !indata[8])
			indata <= $c("({extern unsigned int term_input(); term_input();})");
`else
	always @(posedge clk)
	begin
		sys_odata <= {towrite,data};
		if (didread || !indata[8])
		begin
			indata <= sys_idata;
			sys_tookdata <= 1;
		end else
			sys_tookdata <= 0;
	end
`endif
endmodule