diff options
Diffstat (limited to 'design/slave_dispatcher.v')
| -rw-r--r-- | design/slave_dispatcher.v | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/design/slave_dispatcher.v b/design/slave_dispatcher.v new file mode 100644 index 0000000..8cd0022 --- /dev/null +++ b/design/slave_dispatcher.v @@ -0,0 +1,118 @@ +`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_O, + output wire [15:0] S_COMBINED_DAT_I, + 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 |