1 files changed, 106 insertions, 0 deletions
diff --git a/rtl/src/verilog/eim_arbiter_cdc.v b/rtl/src/verilog/eim_arbiter_cdc.v
new file mode 100644
index 0000000..6a60552
--- /dev/null
+++ b/rtl/src/verilog/eim_arbiter_cdc.v
@@ -0,0 +1,106 @@
+`timescale 1ns / 1ps
+
+module eim_arbiter_cdc
+	(
+		eim_clk, eim_req, eim_ack, eim_din, eim_dout,
+		sys_clk, sys_addr,
+		sys_wren, sys_data_out,
+		sys_rden, sys_data_in
+	);
+	
+
+	input		wire				eim_clk;			// eim clock
+	input		wire				eim_req;			// eim transaction request
+	output	wire				eim_ack;			// eim transaction acknowledge
+	input		wire	[47: 0]	eim_din;			// data from cpu to fpga (write access)
+	output	wire	[31: 0]	eim_dout;		// data from fpga to cpu (read access)
+	
+	input		wire				sys_clk;			// user internal clock
+	output	wire	[13: 0]	sys_addr;		// user access address
+	output	wire				sys_wren;		// user write flag
+	output	wire	[31: 0]	sys_data_out;	// user write data
+	output	wire				sys_rden;		// user read flag
+	input		wire	[31: 0]	sys_data_in;	// user read data
+
+
+		//
+		// EIM_CLK -> SYS_CLK Request
+		//
+	wire				sys_req;		// request pulse in sys_clk clock domain
+	wire	[47: 0]	sys_dout;	// transaction data in sys_clk clock domain
+	
+	cdc_bus_pulse #
+	(
+		.DATA_WIDTH		(48)	// {write, read, addr, data}
+	)
+	cdc_eim_sys
+	(
+		.src_clk			(eim_clk),
+		.src_din			(eim_din),
+		.src_req			(eim_req),
+		
+		.dst_clk			(sys_clk),
+		.dst_dout		(sys_dout),
+		.dst_pulse		(sys_req)
+	);
+	
+	
+		//
+		// Output Registers
+		//
+	reg	[13: 0]	sys_addr_reg		= {14{1'bX}};	//
+	reg				sys_wren_reg		= 1'b0;			//
+	reg	[31: 0]	sys_data_out_reg	= {32{1'bX}};	//
+	reg				sys_rden_reg		= 1'b0;			//
+	
+	assign sys_addr		= sys_addr_reg;
+	assign sys_wren		= sys_wren_reg;
+	assign sys_data_out	= sys_data_out_reg;
+	assign sys_rden		= sys_rden_reg;
+	
+	
+		//
+		// System (User) Clock Access Handler
+		//
+	always @(posedge sys_clk)
+		//
+		if (sys_req) begin									// request detected?
+			sys_wren_reg		<= sys_dout[47];				// set write flag if needed
+			sys_addr_reg		<= sys_dout[45:32];			// set operation address
+			sys_data_out_reg	<= sys_dout[31: 0];			// set data to write
+			sys_rden_reg		<= sys_dout[46];				// set read flag if needed
+		end else begin											// no request active
+			sys_wren_reg		<=  1'b0;						// clear write flag
+			sys_rden_reg		<=  1'b0;						// clear read flag
+		end
+	
+	
+		//
+		// System Request 2-cycle delay to compensate registered mux delay in user-side logic
+		//
+	reg	[ 1: 0]	sys_req_dly		= 2'b00;
+	
+	always @(posedge sys_clk)
+		sys_req_dly <= {sys_req_dly[0], sys_req};
+	
+
+		//
+		// SYS_CLK -> EIM_CLK Acknowledge
+		//	
+	cdc_bus_pulse #
+	(
+		.DATA_WIDTH		(32)	// {data}
+	)
+	cdc_sys_eim
+	(
+		.src_clk			(sys_clk),
+		.src_din			(sys_data_in),
+		.src_req			(sys_req_dly[1]),
+		
+		.dst_clk			(eim_clk),
+		.dst_dout		(eim_dout),
+		.dst_pulse		(eim_ack)
+	);
+
+
+endmodule