cpu: Add processing domains + IMC

Signed-off-by: Ian M. <ian@aptel.org>

4 files changed, 149 insertions, 1 deletions

diff --git a/rtl/cpu/cpu_appdom.sv b/rtl/cpu/cpu_appdom.sv
new file mode 100644
index 0000000..f1e67bb
--- /dev/null
+++ b/rtl/cpu/cpu_appdom.sv
@@ -0,0 +1,25 @@
+//
+// Copyright (c) 2026, Apollo Telephone Laboratories.
+// Provided under the BSD-3 clause.
+//
+
+//
+// Represents a processor application domain
+//
+// @clk_i:          Input clock
+// @reset_i:        Reset input
+// @mb_r_tap<n>_o:  Mainbus request tap output
+//
+module cpu_appdom (
+    input wire clk_i,
+    input wire reset_i,
+
+    output AriFrame mb_r_tap0_o
+);
+    // Lockstep domain 0
+    cpu_lockdom lockdom0 (
+        .clk_i(clk_i),
+        .reset_i(reset_i),
+        .mb_r_tap_o(mb_r_tap0_o)
+    );
+endmodule
diff --git a/rtl/cpu/cpu_imc.sv b/rtl/cpu/cpu_imc.sv
new file mode 100644
index 0000000..2dfca60
--- /dev/null
+++ b/rtl/cpu/cpu_imc.sv
@@ -0,0 +1,79 @@
+//
+// Copyright (c) 2026, Apollo Telephone Laboratories.
+// Provided under the BSD-3 clause.
+//
+
+`include "bus/ari.svh"
+
+//
+// The integrated memory controller (IMC) is responsible for making
+// bus transactions using the address operation tag.
+//
+module cpu_imc (
+    input wire clk_i,
+    input wire reset_i,
+    input wire write_en_i,
+    input wire req_i,
+    input wire [PMA_XLEN-1:0] ad_i,
+    input wire [63:0] data_i,
+
+    output AriFrame mb_r_tap_o,
+    output logic op_done_o
+);
+    parameter FSM_STAGE_REQUEST = 0;
+    parameter FSM_STAGE_TX_REQ  = 1;
+    parameter FSM_STAGE_WAIT0   = 2;
+    parameter FSM_STAGE_WAIT1   = 3;
+    parameter FSM_STAGE_WAIT2   = 4;
+    parameter FSM_STAGE_WAIT3   = 5;
+    parameter FSM_STAGE_DONE    = 6;
+
+    logic [3:0] fsm_stage;
+    logic [3:0] seq;
+    AriAdop adop;
+    AriFrame frame;
+
+    always_ff @(posedge clk_i) begin
+        if (reset_i) begin
+            frame        <= 0;
+            fsm_stage    <= 0;
+            mb_r_tap_o   <= 0;
+            op_done_o    <= 0;
+            seq          <= 0;
+        end else if (req_i || fsm_stage > FSM_STAGE_REQUEST) begin
+            case (fsm_stage)
+                FSM_STAGE_REQUEST: begin
+                    frame.tag       <= ARI_ADOP;
+                    frame.seq       <= seq;
+                    frame.payload   <= adop;
+                    fsm_stage       <= FSM_STAGE_TX_REQ;
+                end
+                FSM_STAGE_TX_REQ: begin
+                    mb_r_tap_o <= frame;
+                    fsm_stage  <= FSM_STAGE_WAIT0;
+                end
+
+                // Four cycle wait period as per the spec
+                FSM_STAGE_WAIT0: fsm_stage <= FSM_STAGE_WAIT1;
+                FSM_STAGE_WAIT1: fsm_stage <= FSM_STAGE_WAIT2;
+                FSM_STAGE_WAIT2: fsm_stage <= FSM_STAGE_WAIT3;
+                FSM_STAGE_WAIT3: fsm_stage <= FSM_STAGE_DONE;
+
+                FSM_STAGE_DONE: begin
+                    mb_r_tap_o  <= 0;
+                    op_done_o   <= 1;
+                    if (!req_i) begin
+                        fsm_stage   <= FSM_STAGE_REQUEST;
+                        op_done_o   <= 0;
+                    end
+                end
+            endcase
+        end
+    end
+
+    // Continous assignments
+    assign adop.ad       = ad_i;
+    assign adop.data     = write_en_i ? data_i : 0;
+    assign adop.write_en = write_en_i;
+    assign adop.reserved = 0;
+endmodule
diff --git a/rtl/cpu/cpu_lockdom.sv b/rtl/cpu/cpu_lockdom.sv
new file mode 100644
index 0000000..81d3d6a
--- /dev/null
+++ b/rtl/cpu/cpu_lockdom.sv
@@ -0,0 +1,37 @@
+//
+// Copyright (c) 2026, Apollo Telephone Laboratories.
+// Provided under the BSD-3 clause.
+//
+
+`include "bus/ari.svh"
+
+//
+// Represents a lockstep domain
+//
+// @clk_i:   Clock input
+// @reset_i:
+//
+module cpu_lockdom (
+    input wire clk_i,
+    input wire reset_i,
+
+    output AriFrame mb_r_tap_o
+);
+    logic imc_write_en = 0;
+    logic imc_req = 0;
+    logic imc_op_done;
+    logic [PMA_XLEN-1:0] imc_ad;
+    logic [63:0] imc_data;
+
+    // Integrated memory controller
+    cpu_imc imc (
+        .clk_i(clk_i),
+        .reset_i(reset_i),
+        .write_en_i(imc_write_en),
+        .req_i(imc_req),
+        .ad_i(imc_ad),
+        .data_i(imc_data),
+        .mb_r_tap_o(mb_r_tap_o),
+        .op_done_o(imc_op_done)
+    );
+endmodule
diff --git a/rtl/soc.sv b/rtl/soc.sv
index f7953a3..2e7442e 100644
--- a/rtl/soc.sv
+++ b/rtl/soc.sv
@@ -34,12 +34,19 @@ module soc (
         .greset_o(greset)
     );
 
+    // Application domain 0
+    cpu_appdom appdom0 (
+        .clk_i(dclk),
+        .reset_i(reset_i),
+        .mb_r_tap0_o(mb_r_tap[0])
+    );
+
     //
     // Zero out currently unused segment taps so that there
     // is no garbage put onto the bus.
     //
     generate
-        for (i = 0; i < ARI_SEGMENT_COUNT; i = i + 1) begin : bus_rst
+        for (i = 1; i < ARI_SEGMENT_COUNT; i = i + 1) begin : bus_rst
             assign mb_r_tap[i] = 0;
         end
     endgenerate