MacPlus_MiSTer/sys/ddr_svc.sv
2020-01-22 00:55:46 +08:00

109 lines
2.6 KiB
Systemverilog

//
// Copyright (c) 2020 Alexey Melnikov
//
//
// This source file is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This source file is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// ------------------------------------------
//
// 16-bit version
module ddr_svc
(
input clk,
input ram_waitrequest,
output [7:0] ram_burstcnt,
output [28:0] ram_addr,
input [63:0] ram_readdata,
input ram_read_ready,
output reg ram_read,
output [63:0] ram_writedata,
output [7:0] ram_byteenable,
output reg ram_write,
output [7:0] ram_bcnt,
input [31:3] ch0_addr,
input [7:0] ch0_burst,
output [63:0] ch0_data,
input ch0_req,
output ch0_ready,
input [31:3] ch1_addr,
input [7:0] ch1_burst,
output [63:0] ch1_data,
input ch1_req,
output ch1_ready
);
assign ram_burstcnt = ram_burst;
assign ram_byteenable = 8'hFF;
assign ram_addr = ram_address;
assign ram_writedata = 0;
assign ch0_data = ram_q[0];
assign ch1_data = ram_q[1];
assign ch0_ready = ready[0];
assign ch1_ready = ready[1];
reg [7:0] ram_burst;
reg [63:0] ram_q[2];
reg [31:3] ram_address;
reg [1:0] ack = 0;
reg [1:0] ready;
reg state = 0;
reg ch = 0;
always @(posedge clk) begin
ready <= 0;
if(!ram_waitrequest) begin
ram_read <= 0;
ram_write <= 0;
case(state)
0: if(ch0_req != ack[0]) begin
ack[0] <= ch0_req;
ram_address <= ch0_addr;
ram_burst <= ch0_burst;
ram_read <= 1;
ch <= 0;
ram_bcnt <= 8'hFF;
state <= 1;
end
else if(ch1_req != ack[1]) begin
ack[1] <= ch1_req;
ram_address <= ch1_addr;
ram_burst <= ch1_burst;
ram_read <= 1;
ch <= 1;
ram_bcnt <= 8'hFF;
state <= 1;
end
1: begin
if(ram_read_ready) begin
ram_bcnt <= ram_bcnt + 1'd1;
ram_q[ch] <= ram_readdata;
ready[ch] <= 1;
if ((ram_bcnt+2'd2) == ram_burst) state <= 0;
end
end
endcase
end
end
endmodule