/*******************************************************************************
 * Module: cmd_encod_linear_wr
 * Date:2015-01-23  
 * Author: andrey     
 * Description: Command sequencer generator for writing a sequential  up to 1KB page
 * single page access, bank and row will not be changed
 *
 * Copyright (c) 2015 <set up in Preferences-Verilog/VHDL Editor-Templates> .
 * cmd_encod_linear_wr.v 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.
 *
 *  cmd_encod_linear_wr.v 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/> .
 *******************************************************************************/
`timescale 1ns/1ps

module  cmd_encod_linear_wr #(
//    parameter BASEADDR = 0,
    parameter ADDRESS_NUMBER=       15,
    parameter COLADDR_NUMBER=       10,
    parameter NUM_XFER_BITS=         6,    // number of bits to specify transfer length
    parameter CMD_PAUSE_BITS=       10,
    parameter CMD_DONE_BIT=         10 // VDT BUG: CMD_DONE_BIT is used in a function call parameter!
) (
    input                        rst,
    input                        clk,
// programming interface
//    input                  [7:0] cmd_ad,      // byte-serial command address/data (up to 6 bytes: AL-AH-D0-D1-D2-D3 
//    input                        cmd_stb,     // strobe (with first byte) for the command a/d
    input                  [2:0] bank_in,     // bank address
    input   [ADDRESS_NUMBER-1:0] row_in,      // memory row
    input   [COLADDR_NUMBER-4:0] start_col,   // start memory column (3 LSBs should be 0?)
    input    [NUM_XFER_BITS-1:0] num128_in,   // number of 128-bit words to transfer (8*16 bits) - full burst of 8 (0 - full 64)
    input                        skip_next_page_in, // do not reset external buffer (continue)    
    input                        start,       // start generating commands
    output reg            [31:0] enc_cmd,     // encoded commnad
    output reg                   enc_wr,      // write encoded command
    output reg                   enc_done     // encoding finished
);
    localparam ROM_WIDTH=13;
    localparam ROM_DEPTH=4;
    
    localparam ENC_NOP=         0;
    localparam ENC_BUF_RD=      1;
    localparam ENC_DQS_TOGGLE=  2;
    localparam ENC_DQ_DQS_EN=   3;
    localparam ENC_SEL=         4;
    localparam ENC_ODT=         5;
    localparam ENC_CMD_SHIFT=   6; // [7:6] - command: 0 -= NOP, 1 - WRITE, 2 - PRECHARGE, 3 - ACTIVATE
    localparam ENC_PAUSE_SHIFT= 8; // [9:8] - 2- bit pause (for NOP commandes)
    localparam ENC_PRE_DONE=   10;
    localparam ENC_BUF_PGNEXT= 11;
    localparam ENC_DUAL_CYC=   12; // 2-cycle command (with nop or skip) to count number of buffer reads (longer pauses are not used  with buffer reads)
    
    localparam ENC_CMD_NOP=      0; // 2-bit locally encoded commands
    localparam ENC_CMD_WRITE=    1;
    localparam ENC_CMD_PRECHARGE=2;
    localparam ENC_CMD_ACTIVATE= 3;
    localparam REPEAT_ADDR=4;
    
    localparam CMD_NOP=      0; // 3-bit normal memory RCW commands (positive logic)
    localparam CMD_WRITE=    3;
    localparam CMD_PRECHARGE=5;
    localparam CMD_ACTIVATE= 4;
    
    reg   [ADDRESS_NUMBER-1:0] row;     // memory row
    reg   [COLADDR_NUMBER-4:0] col;     // start memory column (3 LSBs should be 0?) // VDT BUG: col is used as a function call parameter!
    reg                  [2:0] bank;    // memory bank;
    reg      [NUM_XFER_BITS:0] num128;  // number of 128-bit words to transfer
    reg                        skip_next_page;
    
    reg                        gen_run;
    reg                        gen_run_d;
    reg        [ROM_DEPTH-1:0] gen_addr; // will overrun as stop comes from ROM
    
    reg        [ROM_WIDTH-1:0] rom_r; 
    wire                       pre_done;
    wire                 [1:0] rom_cmd;
    wire                 [1:0] rom_skip;
    wire                 [2:0] full_cmd;
    reg                        done;
//    reg                        buf_rd_23; // read buffer at steps 2&3 (0 if only 1 read is required)
    reg                        start_d;
//    reg        [ROM_DEPTH-1:0] gen_addr_jump; // next conditonal address
    reg     [NUM_XFER_BITS:0] num_bufrd_left; //counts number of buffer reads left
    wire    [NUM_XFER_BITS:0] num_bufrd_left_next_w; //next clock value of the counter
    wire                      next_zero_w=(num_bufrd_left_next_w==0);
    reg                       cut_buf_rd;

    assign     pre_done=rom_r[ENC_PRE_DONE] && gen_run;
    assign     rom_cmd=  rom_r[ENC_CMD_SHIFT+:2];
    assign     rom_skip= rom_r[ENC_PAUSE_SHIFT+:2];
    assign     full_cmd= rom_cmd[1]?(rom_cmd[0]?CMD_ACTIVATE:CMD_PRECHARGE):(rom_cmd[0]?CMD_WRITE:CMD_NOP);
    assign     num_bufrd_left_next_w= num_bufrd_left - (rom_r[ENC_DUAL_CYC]?2:1);
// prepare jump address? and bufrd during 2,3 

// make num128 7-bits to accommodate 64!
    always @ (posedge clk) begin
        start_d <= start;
        if      (start_d)           num_bufrd_left <= {num128[NUM_XFER_BITS-1:0],1'b0};
        else if (rom_r[ENC_BUF_RD]) num_bufrd_left <= num_bufrd_left_next_w;
        cut_buf_rd <= rom_r[ENC_BUF_RD] && (cut_buf_rd || next_zero_w);
    end    
    always @ (posedge rst or posedge clk) begin

        if (rst)           gen_run <= 0;
        else if (start)    gen_run<= 1;
        else if (pre_done) gen_run<= 0;
        
        if (rst)           gen_run_d <= 0;
        else               gen_run_d <= gen_run;

        if (rst)                     gen_addr <= 0;
        else if (!start && !gen_run) gen_addr <= 0;
        else if ((gen_addr==(REPEAT_ADDR-1)) && (num128[NUM_XFER_BITS:1]==0)) gen_addr <= REPEAT_ADDR+1; // skip loop alltogeter
        else if ((gen_addr !=REPEAT_ADDR) || (num128[NUM_XFER_BITS:1]==0)) gen_addr <= gen_addr+1; // not in a loop

//counting loops        
        if      (rst)        num128 <= 0;
        else if (start)      num128 <= {(num128_in==0)?1'b1:1'b0,num128_in};
        else if (!gen_run)   num128 <= 0; //
        else if ((gen_addr == (REPEAT_ADDR-1)) || (gen_addr == REPEAT_ADDR))  num128 <= num128 -1; // ????? - FIXME
    end
    
    always @ (posedge clk) if (start) begin
        row<=row_in;
//        col <= start_col;
        bank <= bank_in;
        skip_next_page <= skip_next_page_in;
    end

    always @ (posedge clk) begin
        if (start) col <= start_col;
        else if (rom_cmd==ENC_CMD_WRITE) col <= col+1;
    end
    
    // ROM-based (registered output) encoded sequence
    // TODO: Remove last ENC_BUF_RD
    always @ (posedge rst or posedge clk) begin
        if (rst)           rom_r <= 0;
        else case (gen_addr)
            4'h0: rom_r <= (ENC_CMD_ACTIVATE <<  ENC_CMD_SHIFT);// | (1 << ENC_NOP); 
            4'h1: rom_r <= (ENC_CMD_NOP <<       ENC_CMD_SHIFT) | (1 << ENC_BUF_RD) | (1 << ENC_PAUSE_SHIFT)                      | (1 << ENC_DUAL_CYC);  // dual cycle
            4'h2: rom_r <= (ENC_CMD_WRITE <<     ENC_CMD_SHIFT) | (1 << ENC_BUF_RD) | (1 << ENC_SEL)         | (1 << ENC_ODT);   // single cycle
            4'h3: rom_r <= (ENC_CMD_NOP <<       ENC_CMD_SHIFT) | (1 << ENC_BUF_RD) | (1 << ENC_DQ_DQS_EN)   | (1 << ENC_ODT);  // single cycle
// next may loop            
            4'h4: rom_r <= (ENC_CMD_WRITE <<     ENC_CMD_SHIFT) | (1 << ENC_NOP) | (1 << ENC_BUF_RD) | (1 << ENC_DQS_TOGGLE)  | (1 << ENC_DQ_DQS_EN) | (1 << ENC_SEL)  | (1 << ENC_ODT) | (1 << ENC_DUAL_CYC);  // dual cycle 
            4'h5: rom_r <= (ENC_CMD_NOP <<       ENC_CMD_SHIFT) | (2 << ENC_PAUSE_SHIFT) | (1 << ENC_DQS_TOGGLE) | (1 << ENC_DQ_DQS_EN) | (1 << ENC_ODT);
            4'h6: rom_r <= (ENC_CMD_NOP <<       ENC_CMD_SHIFT) | (2 << ENC_PAUSE_SHIFT);
            4'h7: rom_r <= (ENC_CMD_PRECHARGE << ENC_CMD_SHIFT) |      (1 << ENC_BUF_PGNEXT);
            4'h8: rom_r <= (ENC_CMD_NOP <<       ENC_CMD_SHIFT) | (2 << ENC_PAUSE_SHIFT);
            4'h9: rom_r <= (ENC_CMD_NOP <<       ENC_CMD_SHIFT) | (1 << ENC_PRE_DONE);
            default:rom_r <= 0;
       endcase
    end
    always @ (posedge rst or posedge clk) begin
        if (rst)           done <= 0;
        else               done <= pre_done;
        
        if (rst)           enc_wr <= 0;
        else               enc_wr <= gen_run || gen_run_d;
        
        if (rst)           enc_done <= 0;
//        else               enc_done <= enc_wr || !gen_run_d;
        else               enc_done <= enc_wr && !gen_run_d;
        
        if (rst)             enc_cmd <= 0;
        else if (rom_cmd==0) enc_cmd <= func_encode_skip ( // encode pause
            {{CMD_PAUSE_BITS-2{1'b0}},rom_skip[1:0]}, // skip;   // number of extra cycles to skip (and keep all the other outputs)
            done,                                     // end of sequence 
            bank[2:0],                                // bank (here OK to be any)
            rom_r[ENC_ODT],          //   odt_en;     // enable ODT
            1'b0,                    //   cke;        // disable CKE
            rom_r[ENC_SEL],          //   sel;        // first/second half-cycle, other will be nop (cke+odt applicable to both)
            rom_r[ENC_DQ_DQS_EN],    //   dq_en;      // enable (not tristate) DQ  lines (internal timing sequencer for 0->1 and 1->0)
            rom_r[ENC_DQ_DQS_EN],    //   dqs_en;     // enable (not tristate) DQS lines (internal timing sequencer for 0->1 and 1->0)
            rom_r[ENC_DQS_TOGGLE],   //   dqs_toggle; // enable toggle DQS according to the pattern
            1'b0,                    //   dci;        // DCI disable, both DQ and DQS lines (internal logic and timing sequencer for 0->1 and 1->0)
            1'b0,                    //   buf_wr;     // connect to external buffer (but only if not paused)
            rom_r[ENC_BUF_RD] && !cut_buf_rd, //buf_rd;// connect to external buffer (but only if not paused)
            rom_r[ENC_BUF_PGNEXT] && !skip_next_page);     //   buf_rst;    // connect to external buffer (but only if not paused)
       else  enc_cmd <= func_encode_cmd ( // encode non-NOP command
            rom_cmd[1]?
                    row:
                    {{ADDRESS_NUMBER-COLADDR_NUMBER{1'b0}},col[COLADDR_NUMBER-4:0],3'b0}, //  [14:0] addr;       // 15-bit row/column adderss
            bank[2:0],                                // bank (here OK to be any)
            full_cmd[2:0],           //   rcw;        // RAS/CAS/WE, positive logic
            rom_r[ENC_ODT],          //   odt_en;     // enable ODT
            1'b0,                    //   cke;        // disable CKE
            rom_r[ENC_SEL],          //   sel;        // first/second half-cycle, other will be nop (cke+odt applicable to both)
            rom_r[ENC_DQ_DQS_EN],    //   dq_en;      // enable (not tristate) DQ  lines (internal timing sequencer for 0->1 and 1->0)
            rom_r[ENC_DQ_DQS_EN],    //   dqs_en;     // enable (not tristate) DQS lines (internal timing sequencer for 0->1 and 1->0)
            rom_r[ENC_DQS_TOGGLE],   //   dqs_toggle; // enable toggle DQS according to the pattern
            1'b0,                    //   dci;        // DCI disable, both DQ and DQS lines (internal logic and timing sequencer for 0->1 and 1->0)
            1'b0,                    //   buf_wr;     // connect to external buffer (but only if not paused)
            rom_r[ENC_BUF_RD] && !cut_buf_rd, //buf_rd;// connect to external buffer (but only if not paused)     
            rom_r[ENC_NOP],          //   nop;        // add NOP after the current command, keep other data
            rom_r[ENC_BUF_PGNEXT] && !skip_next_page);     //   buf_rst;    // connect to external buffer (but only if not paused)
    end    
    

// move to include?
`include "includes/x393_mcontr_encode_cmd.vh" 
endmodule