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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  File name: pci_target32_sm.v                                ////

////                                                              ////

////  This file is part of the "PCI bridge" project               ////

////  http://www.opencores.org/cores/pci/                         ////

////                                                              ////

////  Author(s):                                                  ////

////      - Tadej Markovic, tadej@opencores.org                   ////

////                                                              ////

////  All additional information is avaliable in the README.txt   ////

////  file.                                                       ////

////                                                              ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2000 Tadej Markovic, tadej@opencores.org       ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source 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 Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

//

// CVS Revision History

//

// $Log: not supported by cvs2svn $

// Revision 1.5  2002/08/22 09:07:06  mihad

// Fixed a bug and provided testcase for it. Target was responding to configuration cycle type 1 transactions.

//

// Revision 1.4  2002/02/19 16:32:37  mihad

// Modified testbench and fixed some bugs

//

// Revision 1.3  2002/02/01 15:25:12  mihad

// Repaired a few bugs, updated specification, added test bench files and design document

//

// Revision 1.2  2001/10/05 08:14:30  mihad

// Updated all files with inclusion of timescale file for simulation purposes.

//

// Revision 1.1.1.1  2001/10/02 15:33:47  mihad

// New project directory structure

//

//

`define P_FSM_BITS 2 // number of bits needed for FSM states

`include "pci_constants.v"

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

module PCI_TARGET32_SM

(

    // system inputs

    clk_in,

    reset_in,

    // master inputs

    pci_frame_in,

    pci_irdy_in,

    pci_idsel_in,

    pci_frame_reg_in,

    pci_irdy_reg_in,

    pci_idsel_reg_in,

    // target response outputs

    pci_trdy_out,

    pci_stop_out,

    pci_devsel_out,

    pci_trdy_en_out,

    pci_stop_en_out,

    pci_devsel_en_out,

    ad_load_out,

    ad_load_on_transfer_out,

    // address, data, bus command, byte enable in/outs

    pci_ad_reg_in,

    pci_ad_out,

    pci_ad_en_out,

    pci_cbe_reg_in,

    bckp_trdy_en_in,

    bckp_devsel_in,

    bckp_trdy_in,

    bckp_stop_in,

    pci_trdy_reg_in,

    pci_stop_reg_in,

    // backend side of state machine with control signals to pci_io_mux ...

    address_out,

    addr_claim_in,

    bc_out,

    bc0_out,

    data_out,

    data_in,

    be_out,

    req_out,

    rdy_out,

    addr_phase_out,

    bckp_devsel_out,

    bckp_trdy_out,

    bckp_stop_out,

    last_reg_out,

    frame_reg_out,

    fetch_pcir_fifo_out,

    load_medium_reg_out,

    sel_fifo_mreg_out,

    sel_conf_fifo_out,

    fetch_conf_out,

    load_to_pciw_fifo_out,

    load_to_conf_out,

    same_read_in,

    norm_access_to_config_in,

    read_completed_in,

    read_processing_in,

    target_abort_in,

    disconect_wo_data_in,

    disconect_w_data_in,

    target_abort_set_out,

    pciw_fifo_full_in,

    pcir_fifo_data_err_in,

    wbw_fifo_empty_in,

    wbu_del_read_comp_pending_in,

    wbu_frame_en_in

) ;

/*----------------------------------------------------------------------------------------------------------------------

Various parameters needed for state machine and other stuff

----------------------------------------------------------------------------------------------------------------------*/

parameter       S_IDLE          = 3'b001 ;

parameter       S_WAIT          = 3'b010 ;

parameter       S_TRANSFERE     = 3'b100 ;

/*==================================================================================================================

System inputs.

==================================================================================================================*/

// PCI side clock and reset

input   clk_in,

        reset_in ;

/*==================================================================================================================

PCI interface signals - bidirectional signals are divided to inputs and outputs in I/O cells instantiation

module. Enables are separate signals.

==================================================================================================================*/

// master inputs

input   pci_frame_in,

        pci_irdy_in,

        pci_idsel_in ;

input   pci_frame_reg_in,

        pci_irdy_reg_in,

        pci_idsel_reg_in ;

// target response outputs

output  pci_trdy_out,

        pci_stop_out,

        pci_devsel_out ;

output  pci_trdy_en_out,

        pci_stop_en_out,

        pci_devsel_en_out ;

output  ad_load_out ;

output  ad_load_on_transfer_out ;

// address, data, bus command, byte enable in/outs

input   [31:0]  pci_ad_reg_in ;

output  [31:0]  pci_ad_out ;

output          pci_ad_en_out ;

input   [3:0]   pci_cbe_reg_in ;

input           bckp_trdy_en_in ;

input           bckp_devsel_in ;

input           bckp_trdy_in ;

input           bckp_stop_in ;

input           pci_trdy_reg_in ;

input           pci_stop_reg_in ;

/*==================================================================================================================

Other side of PCI Target state machine

==================================================================================================================*/

// Data, byte enables, bus commands and address ports

output  [31:0]  address_out ;       // current request address output - registered

input           addr_claim_in ;     // current request address claim input

output  [3:0]   bc_out ;            // current request bus command output - registered

output          bc0_out ;           // current cycle RW signal output

input   [31:0]  data_in ;           // for read operations - current dataphase data input

output  [31:0]  data_out ;          // for write operations - current request data output - registered

output   [3:0]  be_out ;            // current dataphase byte enable outputs - registered

// Port connection control signals from PCI FSM

output          req_out ;           // Read is requested to WB master

output          rdy_out ;           // DATA / ADDRESS selection when read or write - registered

output          addr_phase_out ;    // Indicates address phase and also fast-back-to-back address phase - registered

output                  bckp_devsel_out ;       // DEVSEL output (which is registered) equivalent

output          bckp_trdy_out ;     // TRDY output (which is registered) equivalent

output                  bckp_stop_out ;         // STOP output (which is registered) equivalent

output          last_reg_out ;      // Indicates last data phase - registered

output          frame_reg_out ;     // FRAME output signal - registered

output          fetch_pcir_fifo_out ;// Read enable for PCIR_FIFO when when read is finishen on WB side

output          load_medium_reg_out ;// Load data from PCIR_FIFO to medium register (first data must be prepared on time)

output          sel_fifo_mreg_out ; // Read data selection between PCIR_FIFO and medium register

output          sel_conf_fifo_out ; // Read data selection between Configuration registers and "FIFO"

output          fetch_conf_out ;    // Read enable for configuration space registers

output          load_to_pciw_fifo_out ;// Write enable to PCIW_FIFO

output          load_to_conf_out ;  // Write enable to Configuration space registers

/*==================================================================================================================

Status

==================================================================================================================*/

input           same_read_in ;              // Indicates the same read request (important when read is finished on WB side)

input           norm_access_to_config_in ;  // Indicates the access to Configuration space with MEMORY commands

input           read_completed_in ;         // Indicates that read request is completed on WB side

input           read_processing_in ;        // Indicates that read request is processing on WB side

input           target_abort_in ;           // Indicates target abort termination

input           disconect_wo_data_in ;      // Indicates disconnect without data termination

input                   disconect_w_data_in ;           // Indicates disconnect with data termination

input           pciw_fifo_full_in ;         // Indicates that write PCIW_FIFO is full

input           pcir_fifo_data_err_in ;     // Indicates data error on current data read from PCIR_FIFO

input           wbw_fifo_empty_in ;         // Indicates that WB SLAVE UNIT has no data to be written to PCI bus

input                   wbu_del_read_comp_pending_in ; // Indicates that WB SÈAVE UNIT has a delayed read pending

input           wbu_frame_en_in ;           // Indicates that WB SLAVE UNIT is accessing the PCI bus (important if

                                            //   address on PCI bus is also claimed by decoder in this PCI TARGET UNIT

output          target_abort_set_out ;      // Signal used to be set in configuration space registers

/*==================================================================================================================

END of input / output PORT DEFINITONS !!!

==================================================================================================================*/

// Delayed frame signal for determining the address phase

reg             previous_frame ;

// Delayed read completed signal for preparing the data from pcir fifo

reg             read_completed_reg ;

// Delayed disconnect with/without data for stop loading data to PCIW_FIFO

//reg             disconect_wo_data_reg ;

wire config_disconnect ;

wire disconect_wo_data = disconect_wo_data_in || config_disconnect ;

wire disconect_w_data = disconect_w_data_in ;

// Delayed frame signal for determining the address phase!

always@(posedge clk_in or posedge reset_in)

begin

    if (reset_in)

    begin

        previous_frame <= #`FF_DELAY 1'b1 ;

        read_completed_reg <= #`FF_DELAY 1'b0 ;

    end

    else

    begin

        previous_frame <= #`FF_DELAY pci_frame_reg_in ;

        read_completed_reg <= #`FF_DELAY read_completed_in ;

    end

end

// Address phase is when previous frame was 1 and this frame is 0 and frame isn't generated from pci master (in WBU)

wire    addr_phase = (previous_frame && ~pci_frame_reg_in && ~wbu_frame_en_in) ;

`ifdef      HOST

    `ifdef  NO_CNF_IMAGE

            // Wire tells when there is configuration (read or write) command with IDSEL signal active

            wire    config_access = 1'b0 ;

            // Write and read progresses are used for determining next state

            wire    write_progress  =   ( (read_completed_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ||

                                          (~read_processing_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ) ;

            wire    read_progress   =   ( (read_completed_in && wbw_fifo_empty_in) ) ;

    `else

            // Wire tells when there is configuration (read or write) command with IDSEL signal active

            wire    config_access = (pci_idsel_reg_in && pci_cbe_reg_in[3]) && (~pci_cbe_reg_in[2] && pci_cbe_reg_in[1]) &&     // idsel asserted with correct bus command(101x)

                                    (pci_ad_reg_in[1:0] == 2'b00) ;        // has to be type 0 configuration cycle

            // Write and read progresses are used for determining next state

            wire    write_progress  =   ( (norm_access_to_config_in) ||

                                                                  (read_completed_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ||

                                          (~read_processing_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ) ;

            wire    read_progress   =   ( (~read_completed_in && norm_access_to_config_in) ||

                                          (read_completed_in && wbw_fifo_empty_in) ) ;

    `endif

`else

            // Wire tells when there is configuration (read or write) command with IDSEL signal active

            wire    config_access = (pci_idsel_reg_in && pci_cbe_reg_in[3]) && (~pci_cbe_reg_in[2] && pci_cbe_reg_in[1]) &&     // idsel asserted with correct bus command(101x)

                                    (pci_ad_reg_in[1:0] == 2'b00) ;        // has to be type 0 configuration cycle

            // Write and read progresses are used for determining next state

            wire    write_progress  =   ( (norm_access_to_config_in) ||

                                                                  (read_completed_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ||

                                          (~read_processing_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ) ;

            wire    read_progress   =   ( (~read_completed_in && norm_access_to_config_in) ||

                                          (read_completed_in && wbw_fifo_empty_in) ) ;

`endif

// Signal for loading data to medium register from pcir fifo when read completed from WB side!

wire    prepare_rd_fifo_data = (read_completed_in && ~read_completed_reg) ;

// Write allowed to PCIW_FIFO

wire    write_to_fifo   =   ((read_completed_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in) ||

                                                         (~read_processing_in && ~pciw_fifo_full_in && ~wbu_del_read_comp_pending_in)) ;

// Read allowed from PCIR_FIFO

wire    read_from_fifo  =   (read_completed_in && wbw_fifo_empty_in) ;

`ifdef      HOST

    `ifdef  NO_CNF_IMAGE

            // Read request is allowed to be proceed regarding the WB side

            wire    read_request    =   (~read_completed_in && ~read_processing_in) ;

    `else

            // Read request is allowed to be proceed regarding the WB side

            wire    read_request    =   (~read_completed_in && ~read_processing_in && ~norm_access_to_config_in) ;

    `endif

`else

            // Read request is allowed to be proceed regarding the WB side

            wire    read_request    =   (~read_completed_in && ~read_processing_in && ~norm_access_to_config_in) ;

`endif

// Critically calculated signals are latched in this clock period (address phase) to be used in the next clock period

reg             rw_cbe0 ;

reg             wr_progress ;

reg             rd_progress ;

reg             rd_from_fifo ;

reg             rd_request ;

reg             wr_to_fifo ;

reg             same_read_reg ;

always@(posedge clk_in or posedge reset_in)

begin

    if (reset_in)

    begin

        rw_cbe0                         <= #`FF_DELAY 1'b0 ;

        wr_progress                     <= #`FF_DELAY 1'b0 ;

        rd_progress                     <= #`FF_DELAY 1'b0 ;

        rd_from_fifo                    <= #`FF_DELAY 1'b0 ;

        rd_request                      <= #`FF_DELAY 1'b0 ;

        wr_to_fifo                      <= #`FF_DELAY 1'b0 ;

        same_read_reg                   <= #`FF_DELAY 1'b0 ;

    end

    else

    begin

        if (addr_phase)

        begin

            rw_cbe0                     <= #`FF_DELAY pci_cbe_reg_in[0] ;

            wr_progress                 <= #`FF_DELAY write_progress ;

            rd_progress                 <= #`FF_DELAY read_progress ;

            rd_from_fifo                <= #`FF_DELAY read_from_fifo ;

            rd_request                  <= #`FF_DELAY read_request ;

            wr_to_fifo                  <= #`FF_DELAY write_to_fifo ;

            same_read_reg               <= #`FF_DELAY same_read_in ;

        end

    end

end

`ifdef      HOST

    `ifdef  NO_CNF_IMAGE

            wire    norm_access_to_conf_reg     = 1'b0 ;

            wire    cnf_progress                = 1'b0 ;

    `else

            reg     norm_access_to_conf_reg ;

            reg     cnf_progress ;

            always@(posedge clk_in or posedge reset_in)

            begin

                if (reset_in)

                begin

                    norm_access_to_conf_reg     <= #`FF_DELAY 1'b0 ;

                    cnf_progress                <= #`FF_DELAY 1'b0 ;

                end

                else

                begin

                    if (addr_phase)

                    begin

                        norm_access_to_conf_reg <= #`FF_DELAY norm_access_to_config_in ;

                        cnf_progress            <= #`FF_DELAY config_access ;

                    end

                end

            end

    `endif

`else

            reg     norm_access_to_conf_reg ;

            reg     cnf_progress ;

            always@(posedge clk_in or posedge reset_in)

            begin

                if (reset_in)

                begin

                    norm_access_to_conf_reg     <= #`FF_DELAY 1'b0 ;

                    cnf_progress                <= #`FF_DELAY 1'b0 ;

                end

                else

                begin

                    if (addr_phase)

                    begin

                        norm_access_to_conf_reg <= #`FF_DELAY norm_access_to_config_in ;

                        cnf_progress            <= #`FF_DELAY config_access ;

                    end

                end

            end

`endif

// Signal used in S_WAIT state to determin next state

wire s_wait_progress =  (

                        (~cnf_progress && rw_cbe0 && wr_progress && ~target_abort_in) ||

                        (~cnf_progress && ~rw_cbe0 && same_read_reg && rd_progress && ~target_abort_in && ~pcir_fifo_data_err_in) ||

                        (~cnf_progress && ~rw_cbe0 && ~same_read_reg && norm_access_to_conf_reg && ~target_abort_in) ||

                        (cnf_progress && ~target_abort_in)

                        ) ;

// Signal used in S_TRANSFERE state to determin next state

wire s_tran_progress =  (

                        (rw_cbe0 && !disconect_wo_data) ||

                        (~rw_cbe0 && !disconect_wo_data && !target_abort_in && !pcir_fifo_data_err_in)

                        ) ;

// Clock enable for PCI state machine driven directly from critical inputs - FRAME and IRDY

wire            pcit_sm_clk_en ;

// FSM states signals indicating the current state

reg             state_idle ;

reg             state_wait ;

reg             sm_transfere ;

reg             backoff ;

reg             state_default ;

wire            state_backoff   = sm_transfere && backoff ;

wire            state_transfere = sm_transfere && !backoff ;

always@(posedge clk_in or posedge reset_in)

begin

    if ( reset_in )

        backoff <= #`FF_DELAY 1'b0 ;

    else if ( state_idle )

        backoff <= #`FF_DELAY 1'b0 ;

    else

        backoff <= #`FF_DELAY (state_wait && !s_wait_progress) ||

                              (sm_transfere && !s_tran_progress && !pci_frame_in && !pci_irdy_in) ||

                              backoff ;

end

assign config_disconnect = sm_transfere && (norm_access_to_conf_reg || cnf_progress) ;

// Clock enable module used for preserving the architecture because of minimum delay for critical inputs

PCI_TARGET32_CLK_EN         pci_target_clock_en

(

    .addr_phase             (addr_phase),

    .config_access          (config_access),

    .addr_claim_in          (addr_claim_in),

    .pci_frame_in           (pci_frame_in),

    .state_wait             (state_wait),

    .state_transfere        (sm_transfere),

    .state_default          (state_default),

    .clk_enable             (pcit_sm_clk_en)

);

reg [(`P_FSM_BITS - 1):0]  c_state ; //current state register

reg [(`P_FSM_BITS - 1):0]  n_state ; //next state input to current state register

// state machine register control

always@(posedge clk_in or posedge reset_in)

begin

    if (reset_in) // reset state machine to S_IDLE state

        c_state <= #`FF_DELAY S_IDLE ;

    else

        if (pcit_sm_clk_en) // if conditions are true, then FSM goes to next state!

            c_state <= #`FF_DELAY n_state ;

end

// state machine logic

always@(c_state)

begin

    case (c_state)

    S_IDLE :

    begin

        state_idle      <= 1'b1 ;

        state_wait      <= 1'b0 ;

        sm_transfere <= 1'b0 ;

        state_default   <= 1'b0 ;

        n_state <= S_WAIT ;

    end

    S_WAIT :

    begin

        state_idle      <= 1'b0 ;

        state_wait      <= 1'b1 ;

        sm_transfere <= 1'b0 ;

        state_default   <= 1'b0 ;

        n_state <= S_TRANSFERE ;

    end

    S_TRANSFERE :

    begin

        state_idle      <= 1'b0 ;

        state_wait      <= 1'b0 ;

        sm_transfere <= 1'b1 ;

        state_default   <= 1'b0 ;

        n_state <= S_IDLE ;

    end

    default :

    begin

        state_idle      <= 1'b0 ;

        state_wait      <= 1'b0 ;

        sm_transfere <= 1'b0 ;

        state_default   <= 1'b1 ;

        n_state <= S_IDLE ;

    end

    endcase

end

        // if not retry and not target abort

        // NO CRITICAL SIGNALS

wire    trdy_w          =   (

        (state_wait && ~cnf_progress && rw_cbe0 && wr_progress && ~target_abort_in) ||

        (state_wait && ~cnf_progress && ~rw_cbe0 && same_read_reg && rd_progress && ~target_abort_in && !pcir_fifo_data_err_in) ||

        (state_wait && ~cnf_progress && ~rw_cbe0 && ~same_read_reg && norm_access_to_conf_reg && ~target_abort_in) ||

        (state_wait && cnf_progress && ~target_abort_in)

                            ) ;

        // if not disconnect without data and not target abort (only during reads)

        // MUST BE ANDED WITH CRITICAL ~FRAME

wire    trdy_w_frm      =   (

        (state_transfere && !cnf_progress && !norm_access_to_conf_reg && rw_cbe0 && !disconect_wo_data) ||

        (state_transfere && !cnf_progress && !norm_access_to_conf_reg && ~rw_cbe0 && !disconect_wo_data && ~pcir_fifo_data_err_in) ||

        (state_transfere && !cnf_progress && !norm_access_to_conf_reg && disconect_w_data && pci_irdy_reg_in && (rw_cbe0 || !pcir_fifo_data_err_in))

                            ) ;

        // if not disconnect without data and not target abort (only during reads)

        // MUST BE ANDED WITH CRITICAL ~FRAME AND IRDY

wire    trdy_w_frm_irdy =   ( ~bckp_trdy_in ) ;

// TRDY critical module used for preserving the architecture because of minimum delay for critical inputs

PCI_TARGET32_TRDY_CRIT      pci_target_trdy_critical

(

    .trdy_w                 (trdy_w),

    .trdy_w_frm             (trdy_w_frm),

    .trdy_w_frm_irdy        (trdy_w_frm_irdy),

    .pci_frame_in           (pci_frame_in),

    .pci_irdy_in            (pci_irdy_in),

    .pci_trdy_out           (pci_trdy_out)

);

        // if target abort or retry

        // NO CRITICAL SIGNALS

wire    stop_w          =   (

        (state_wait && target_abort_in) ||

        (state_wait && ~cnf_progress && rw_cbe0 && ~wr_progress) ||

        (state_wait && ~cnf_progress && ~rw_cbe0 && same_read_reg && ~rd_progress) ||

        (state_wait && ~cnf_progress && ~rw_cbe0 && same_read_reg && rd_progress && pcir_fifo_data_err_in) ||

        (state_wait && ~cnf_progress && ~rw_cbe0 && ~same_read_reg && ~norm_access_to_conf_reg)

                            ) ;

        // if asserted, wait for deactivating the frame

        // MUST BE ANDED WITH CRITICAL ~FRAME

wire    stop_w_frm      =   (

        (state_backoff && ~bckp_stop_in)

                            ) ;

        // if target abort or if disconnect without data (after data transfere)

        // MUST BE ANDED WITH CRITICAL ~FRAME AND ~IRDY

wire    stop_w_frm_irdy =   (

        (state_transfere && (disconect_wo_data)) ||

        (state_transfere && ~rw_cbe0 && pcir_fifo_data_err_in)

                            ) ;

// STOP critical module used for preserving the architecture because of minimum delay for critical inputs

PCI_TARGET32_STOP_CRIT      pci_target_stop_critical

(

    .stop_w                 (stop_w),

    .stop_w_frm             (stop_w_frm),

    .stop_w_frm_irdy        (stop_w_frm_irdy),

    .pci_frame_in           (pci_frame_in),

    .pci_irdy_in            (pci_irdy_in),

    .pci_stop_out           (pci_stop_out)

);

        // if OK to respond and not target abort

        // NO CRITICAL SIGNALS

wire    devs_w          =   (

        (addr_phase && config_access) ||

        (addr_phase && ~config_access && addr_claim_in) ||

        (state_wait && ~target_abort_in && !(~cnf_progress && ~rw_cbe0 && same_read_reg && rd_progress && pcir_fifo_data_err_in) )

                            ) ;

        // if not target abort (only during reads) or if asserted, wait for deactivating the frame

        // MUST BE ANDED WITH CRITICAL ~FRAME

wire    devs_w_frm      =   (

        (state_transfere && rw_cbe0) ||

        (state_transfere && ~rw_cbe0 && ~pcir_fifo_data_err_in) ||

        (state_backoff && ~bckp_devsel_in)

                            ) ;

        // if not target abort (only during reads)

        // MUST BE ANDED WITH CRITICAL ~FRAME AND IRDY

wire    devs_w_frm_irdy =   (

        (state_transfere && ~rw_cbe0 && pcir_fifo_data_err_in)

                            ) ;

// DEVSEL critical module used for preserving the architecture because of minimum delay for critical inputs

PCI_TARGET32_DEVS_CRIT      pci_target_devsel_critical

(

    .devs_w                 (devs_w),

    .devs_w_frm             (devs_w_frm),

    .devs_w_frm_irdy        (devs_w_frm_irdy),

    .pci_frame_in           (pci_frame_in),

    .pci_irdy_in            (pci_irdy_in),

    .pci_devsel_out         (pci_devsel_out)

);

// signal used in AD enable module with preserving the hierarchy because of minimum delay for critical inputs

assign  pci_ad_en_out =    (

        (addr_phase && config_access && ~pci_cbe_reg_in[0]) ||

        (addr_phase && ~config_access && addr_claim_in && ~pci_cbe_reg_in[0]) ||

        (state_wait && ~rw_cbe0) ||

        (state_transfere && ~rw_cbe0) ||

        (state_backoff && ~rw_cbe0 && ~pci_frame_reg_in)

                            ) ;

wire fast_back_to_back  =   (addr_phase && ~pci_irdy_reg_in) ;

        // if cycle will progress or will not be stopped

        // NO CRITICAL SIGNALS

wire    ctrl_en       =

        /*(~wbu_frame_en_in && fast_back_to_back) ||*/

        (addr_phase && config_access) ||

        (addr_phase && ~config_access && addr_claim_in) ||

        (state_wait) ||

        (state_transfere && ~(pci_frame_reg_in && ~pci_irdy_reg_in && (~pci_stop_reg_in || ~pci_trdy_reg_in))) ||

        (state_backoff && ~(pci_frame_reg_in && ~pci_irdy_reg_in && (~pci_stop_reg_in || ~pci_trdy_reg_in))) ;

assign pci_trdy_en_out   = ctrl_en ;

assign pci_stop_en_out   = ctrl_en ;

assign pci_devsel_en_out = ctrl_en ;

// target ready output signal delayed for one clock used in conjunction with irdy_reg to select which

//   data are registered in io mux module - from fifo or medoum register

reg             bckp_trdy_reg ;

// delayed indicators for states transfere and backoff

reg             state_transfere_reg ;

reg             state_backoff_reg ;

always@(posedge clk_in or posedge reset_in)

begin

    if (reset_in)

    begin

        bckp_trdy_reg <= #`FF_DELAY 1'b1 ;

        state_transfere_reg <= #`FF_DELAY 1'b0 ;

        state_backoff_reg <= #`FF_DELAY 1'b0 ;

    end

    else

    begin

        bckp_trdy_reg <= #`FF_DELAY bckp_trdy_in ;

        state_transfere_reg <= #`FF_DELAY state_transfere ;

        state_backoff_reg <= #`FF_DELAY state_backoff ;

    end

end

// Read control signals assignments

assign

    fetch_pcir_fifo_out =   (

        (prepare_rd_fifo_data) ||

        (state_wait && ~cnf_progress && ~rw_cbe0 && same_read_reg && rd_from_fifo && ~target_abort_in) ||

        (bckp_trdy_en_in && ~pci_trdy_reg_in && ~cnf_progress && ~rw_cbe0 && same_read_reg && rd_from_fifo && ~pci_irdy_reg_in)

                            ) ;

assign  ad_load_out         =   (state_wait) ;

assign  ad_load_on_transfer_out = (bckp_trdy_en_in && ~rw_cbe0) ;

assign  load_medium_reg_out =   (

        (prepare_rd_fifo_data) ||

        (state_wait && ~rw_cbe0 && ~cnf_progress && same_read_reg && rd_from_fifo && ~target_abort_in) ||

        (~pci_irdy_reg_in && ~rw_cbe0 && ~cnf_progress && same_read_reg && rd_from_fifo && ~pci_trdy_reg_in && bckp_trdy_en_in)

                                ) ;

assign  sel_fifo_mreg_out = (~pci_irdy_reg_in && ~bckp_trdy_reg) ;

`ifdef      HOST

    `ifdef  NO_CNF_IMAGE

            assign  sel_conf_fifo_out = 1'b0 ;

    `else

            assign  sel_conf_fifo_out = (cnf_progress || norm_access_to_conf_reg) ;