module sbtm2 (input logic [11:0] a, output logic [10:0] y);

   // bit partitions
   logic [4:0] x0;
   logic [2:0] x1;
   logic [3:0] x2;
   logic [2:0] x2_1cmp;   
   // mem outputs
   logic [12:0] y0;
   logic [5:0] 	y1;
   // input to CPA
   logic [14:0] op1;
   logic [14:0] op2;
   logic [14:0] p; 
   logic cout;  

   assign x0 = a[11:7];
   assign x1 = a[6:4];
   assign x2 = a[3:0];   

   sbtm_a2 mem1 ({x0[3:0], x1}, y0);
   assign op1 = {1'b0, y0, 1'b0};
   
   // 1s cmp per sbtm/stam
   assign x2_1cmp = x2[3] ? ~x2[2:0] : x2[2:0];   
   sbtm_a3 mem2 ({x0, x2_1cmp}, y1);
   // 1s cmp per sbtm/stam
   assign op2 = x2[3] ? {{8{1'b1}}, ~y1, 1'b1} :
		{8'b0, y1, 1'b1};
   
   // CPA
   bk15 cp1 (cout, p, op1, op2, 1'b0);
   assign y = p[14:4];

endmodule // sbtm2