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`default_nettype none
module slave_dispatcher
(
input wire CLK,
input wire RST,
input wire S0_ACK_O,
output wire [17:0] S0_ADR_I,
output wire [15:0] S0_DAT_I,
input wire [15:0] S0_DAT_O,
output wire S0_STB_I,
output wire S0_WE_I,
input wire S0_STALL_O,
input wire S1_ACK_O,
output wire [17:0] S1_ADR_I,
output wire [15:0] S1_DAT_I,
input wire [15:0] S1_DAT_O,
output wire S1_STB_I,
output wire S1_WE_I,
input wire S1_STALL_O,
input wire S2_ACK_O,
output wire [17:0] S2_ADR_I,
output wire [15:0] S2_DAT_I,
input wire [15:0] S2_DAT_O,
output wire S2_STB_I,
output wire S2_WE_I,
input wire S2_STALL_O,
input wire S3_ACK_O,
output wire [17:0] S3_ADR_I,
output wire [15:0] S3_DAT_I,
input wire [15:0] S3_DAT_O,
output wire S3_STB_I,
output wire S3_WE_I,
input wire S3_STALL_O,
output wire S_COMBINED_ACK_O,
input wire [19:0] S_COMBINED_ADR_I,
input wire [15:0] S_COMBINED_DAT_I,
output wire [15:0] S_COMBINED_DAT_O,
input wire S_COMBINED_STB_I,
input wire S_COMBINED_WE_I,
output wire S_COMBINED_STALL_O
);
wire [0:3] acks;
wire [0:3] stalls;
wire [15:0] datas [0:3];
assign acks = {S0_ACK_O, S1_ACK_O, S2_ACK_O, S3_ACK_O};
assign stalls = {S0_STALL_O, S1_STALL_O, S2_STALL_O, S3_STALL_O};
assign datas[0] = S0_DAT_O;
assign datas[1] = S1_DAT_O;
assign datas[2] = S2_DAT_O;
assign datas[3] = S3_DAT_O;
reg [1:0] commands_awaiting;
reg [1:0] slave_last_accessed;
wire working;
wire [1:0] slave_accessed;
wire slave_switch;
wire [1:0] commands_awaiting_next_tick;
assign working = commands_awaiting || S_COMBINED_STB_I;
assign slave_accessed = commands_awaiting ? slave_last_accessed :
S_COMBINED_ADR_I[19:18];
assign S_COMBINED_ACK_O = acks[slave_accessed] && working;
assign S_COMBINED_DAT_O = datas[slave_accessed];
assign slave_switch = slave_accessed != S_COMBINED_ADR_I[19:18];
assign S_COMBINED_STALL_O = stalls[slave_accessed] || slave_switch ||
(commands_awaiting == 3 && !S_COMBINED_ACK_O);
assign commands_awaiting_next_tick
= commands_awaiting - S_COMBINED_ACK_O +
(S_COMBINED_STB_I && !S_COMBINED_STALL_O);
`ifdef SIMULATION
/* anything could be latched here, this is just to avoid undefined values */
initial begin
slave_last_accessed <= 0;
commands_awaiting <= 2; /* It is supposed to be driven low by RST */
end
`endif
always @ (posedge CLK) begin
slave_last_accessed <= slave_accessed;
if (RST)
commands_awaiting <= 0;
else
commands_awaiting <= commands_awaiting_next_tick;
end
assign S0_ADR_I = S_COMBINED_ADR_I[17:0];
assign S1_ADR_I = S_COMBINED_ADR_I[17:0];
assign S2_ADR_I = S_COMBINED_ADR_I[17:0];
assign S3_ADR_I = S_COMBINED_ADR_I[17:0];
assign S0_DAT_I = S_COMBINED_DAT_I;
assign S1_DAT_I = S_COMBINED_DAT_I;
assign S2_DAT_I = S_COMBINED_DAT_I;
assign S3_DAT_I = S_COMBINED_DAT_I;
wire pass_strobe;
assign pass_strobe = S_COMBINED_STB_I && !slave_switch &&
(commands_awaiting != 3 || S_COMBINED_ACK_O);
assign S0_STB_I = slave_accessed == 0 && pass_strobe;
assign S1_STB_I = slave_accessed == 1 && pass_strobe;
assign S2_STB_I = slave_accessed == 2 && pass_strobe;
assign S3_STB_I = slave_accessed == 3 && pass_strobe;
assign S0_WE_I = S_COMBINED_WE_I;
assign S1_WE_I = S_COMBINED_WE_I;
assign S2_WE_I = S_COMBINED_WE_I;
assign S3_WE_I = S_COMBINED_WE_I;
endmodule // slave_dispatcher
|
