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module bus_master
(
input logic clk,
rst_n,
input logic[29:0] addr,
input logic start,
write,
output logic ready,
output logic[31:0] data_rd,
input logic[31:0] data_wr,
output logic cpu_clk,
cpu_rst_n,
irq,
output logic[31:0] avl_address,
output logic avl_read,
avl_write,
input logic[31:0] avl_readdata,
output logic[31:0] avl_writedata,
input logic avl_waitrequest,
output logic[3:0] avl_byteenable,
input logic avl_irq
);
enum {
IDLE,
WAIT
} state;
assign irq = avl_irq;
assign cpu_clk = clk;
assign cpu_rst_n = rst_n;
assign data_rd = avl_readdata;
assign avl_byteenable = 4'b1111; //TODO
always_comb
unique case(state)
IDLE: ready = 0;
WAIT: ready = !avl_waitrequest;
endcase
always_ff @(posedge clk or negedge rst_n)
/* P. 16:
* A host must make no assumption about the assertion state of
* waitrequest when the host is idle: waitrequest may be high or
* low, depending on system properties. When waitrequest is asserted,
* host control signals to the agent must remain constant except for
* beginbursttransfer.
*/
if(!rst_n) begin
state <= IDLE;
avl_read <= 0;
avl_write <= 0;
avl_address <= 0;
avl_writedata <= 0;
end else if((state == IDLE || !avl_waitrequest) && start) begin
state <= WAIT;
avl_read <= ~write;
avl_write <= write;
avl_address <= {addr, 2'b00};
avl_writedata <= data_wr;
end else if(state == WAIT && !avl_waitrequest) begin
state <= IDLE;
avl_read <= 0;
avl_write <= 0;
end
endmodule
|
