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/**********************************************************************************

*                                                                                                                                                                                                                                                                                                                                       *

*               BiDirectional Cell:                                                                                                                                                                                                                                             *

*                                                                                                                                                                                                                                                                                                                                       *

*               FromCore: Value that comes from on-chip logic and goes to pin                                                                   *

*               ToCore: Value that is read-in from the pin and goes to core                                                                             *

*               FromPreviousBSCell: Value from previous boundary scan cell                                                                              *

*               ToNextBSCell: Value for next boundary scan cell                                                                                                                         *

*               CaptureDR, ShiftDR, UpdateDR: TAP states                                                                                                                                                        *

*               extest: Instruction Register Command                                                                                                                                                                    *

*               TCK: Test Clock                                                                                                                                                                                                                                                         *

*               BiDirPin: Bidirectional pin connected to this BS cell                                                                                                   *

*               FromOutputEnable: This pin comes from core or ControlCell                                                                                       *

*                                                                                                                                                                                                                                                                                                                                       *

*               Signal that is connected to BiDirPin comes from core or BS chain. Tristate              *

*               control is generated in core or BS chain (ControlCell).                                                                                         *

*                                                                                                                                                                                                                                                                                                                                       *

**********************************************************************************/

module BiDirectionalCell( FromCore, ToCore, FromPreviousBSCell, CaptureDR, ShiftDR, UpdateDR, extest, TCK, ToNextBSCell, FromOutputEnable, BiDirPin);

input  FromCore;

input  FromPreviousBSCell;

input  CaptureDR;

input  ShiftDR;

input  UpdateDR;

input  extest;

input  TCK;

input  FromOutputEnable;

reg Latch;

output ToNextBSCell;

reg    ToNextBSCell;

output BiDirPin;

output ToCore;

reg  ShiftedControl;

wire SelectedInput = CaptureDR? BiDirPin : FromPreviousBSCell;

always @ (posedge TCK)

begin

        if(CaptureDR | ShiftDR)

                Latch<=SelectedInput;

end

always @ (negedge TCK)

begin

        ToNextBSCell<=Latch;

end

always @ (negedge TCK)

begin

        if(UpdateDR)

                ShiftedControl<=ToNextBSCell;

end

wire MuxedSignal = extest? ShiftedControl : FromCore;

assign BiDirPin = FromOutputEnable? MuxedSignal : 1'bz;

//BUF Buffer (.I(BiDirPin), .O(ToCore));

assign ToCore = BiDirPin;

endmodule       // TristateCell