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// ========== Copyright Header Begin ==========================================

// 

// OpenSPARC T1 Processor File: test_stub_scan.v

// Copyright (c) 2006 Sun Microsystems, Inc.  All Rights Reserved.

// DO NOT ALTER OR REMOVE COPYRIGHT NOTICES.

// 

// The above named program is free software; you can redistribute it and/or

// modify it under the terms of the GNU General Public

// License version 2 as published by the Free Software Foundation.

// 

// The above named program 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 work; if not, write to the Free Software

// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.

// 

// ========== Copyright Header End ============================================

// ____________________________________________________________________________

//

//  test_stub_bist - Test Stub with Scan Support

// ____________________________________________________________________________

//

// Description: DBB interface for test signal generation

// ____________________________________________________________________________

module test_stub_scan (/*AUTOARG*/

// Outputs

mux_drive_disable, mem_write_disable, sehold, se, testmode_l,

mem_bypass, so_0, so_1, so_2,

// Inputs

ctu_tst_pre_grst_l, arst_l, global_shift_enable,

ctu_tst_scan_disable, ctu_tst_scanmode, ctu_tst_macrotest,

ctu_tst_short_chain, long_chain_so_0, short_chain_so_0,

long_chain_so_1, short_chain_so_1, long_chain_so_2, short_chain_so_2

);

   input        ctu_tst_pre_grst_l;

   input        arst_l;                // no longer used

   input        global_shift_enable;

   input        ctu_tst_scan_disable;  // redefined as pin_based_scan

   input        ctu_tst_scanmode;

   input        ctu_tst_macrotest;

   input        ctu_tst_short_chain;

   input        long_chain_so_0;

   input        short_chain_so_0;

   input        long_chain_so_1;

   input        short_chain_so_1;

   input        long_chain_so_2;

   input        short_chain_so_2;

   output       mux_drive_disable;

   output       mem_write_disable;

   output       sehold;

   output       se;

   output       testmode_l;

   output       mem_bypass;

   output       so_0;

   output       so_1;

   output       so_2;

   wire         pin_based_scan;

   wire         short_chain_en;

   wire         short_chain_select;

   // INTERNAL CLUSTER CONNECTIONS

   //

   // Scan Chain Hookup

   // =================

   //

   // Scan chains have two configurations: long and short.

   // The short chain is typically the first tenth of the

   // long chain. The short chain should contain memory

   // collar flops for deep arrays. The CTU determines

   // which configuration is selected. Up to three chains

   // are supported.

   //

   // The scanout connections from the long and short

   // chains connect to the following inputs:

   //

   // long_chain_so_0, short_chain_so_0 (mandatory)

   // long_chain_so_1, short_chain_so_1 (optional)

   // long_chain_so_2, short_chain_so_2 (optional)

   //

   // The test stub outputs should connect directly to the

   // scanout port(s) of the cluster:

   //

   // so_0 (mandatory), so_1 (optional), so_2 (optional)

   //

   //

   // Static Output Signals

   // =====================

   //

   // testmode_l

   //

   // Local testmode control for overriding gated

   // clocks, asynchronous resets, etc. Asserted

   // for all shift-based test modes.

   //

   // mem_bypass

   //

   // Memory bypass control for arrays without output

   // flops. Allows testing of shadow logic. Asserted

   // for scan test; de-asserted for macrotest.

   //

   //

   // Dynamic Output Signals

   // ======================

   //

   // sehold

   //

   // The sehold signal needs to be set for macrotest

   // to allow holding flops in the array collars

   // to retain their shifted data during capture.

   // Inverted version of scan enable during macrotest.

   //

   // mux_drive_disable (for mux/long chain protection)

   //

   // Activate one-hot mux protection circuitry during

   // scan shift and reset. Formerly known as rst_tri_en.

   // Also used by long chain memories with embedded

   // control.

   //

   // mem_write_disable (for short chain protection)

   //

   // Protects contents of short chain memories during

   // shift and POR.

   //

   // se

   assign  mux_drive_disable  = ~ctu_tst_pre_grst_l | short_chain_select | se;

   assign  mem_write_disable  = ~ctu_tst_pre_grst_l | se;

   assign  sehold             = ctu_tst_macrotest & ~se;

   assign  se                 = global_shift_enable;

   assign  testmode_l         = ~ctu_tst_scanmode;

   assign  mem_bypass         = ~ctu_tst_macrotest & ~testmode_l;

   assign  pin_based_scan     = ctu_tst_scan_disable;

   assign  short_chain_en     = ~(pin_based_scan & se);

   assign  short_chain_select = ctu_tst_short_chain & ~testmode_l & short_chain_en;

   assign  so_0               = short_chain_select ? short_chain_so_0 : long_chain_so_0;

   assign  so_1               = short_chain_select ? short_chain_so_1 : long_chain_so_1;

   assign  so_2               = short_chain_select ? short_chain_so_2 : long_chain_so_2;

endmodule // test_stub_scan