zero_gravity

Storm Core (ARM7 compatible)

Hi,

doing a simple test, I noticed that doing a branch there was an X propagating in the circuit. Following on a schematic the root cause was a conflicting assignment within Barrel Shifter. Hereafter the proposed solution as a patch. Hope this can help

Cheers
Andrea

If you want to contact me use: aconcil@alice.it


================================
*** Z:\work\sp_1300B\SP_1300B\FE\IPs_EVAL\STANDALONE\lib\STORM_CORE\hdl\src\storm_core\storm_core\trunk\VHDL_source\BARREL_SHIFTER.vhd 2011-06-05 17:59:24.000000000 +-0200
--- Z:\work\sp_1300B\SP_1300B\FE\IPs_EVAL\STANDALONE\lib\STORM_CORE\hdl\src\storm_core\storm_core\trunk\src\BARREL_SHIFTER.vhd 2011-08-22 15:37:22.000000000 +-0200
***************
*** 80,92 ****
  					else -- ROR #shift_positions
  						SHIFT_DATA <= to_StdLogicVector(to_BitVector(SHIFT_DATA_IN) ror shift_positions);
  						CARRY_OUT  <= SHIFT_DATA_IN(shift_positions - 1);
  					end if;
  
  				when others => -- undefined
! 					SHIFT_DATA_OUT <= (others => '-');
  					CARRY_OUT      <= '-';
  			end case;
  			
  			if (STORM_MODE = TRUE) then -- use cool overflow feature
  				if (SHIFT_MODE = S_LSL) then -- overflow detection
  					OVERFLOW_OUT <= SHIFT_DATA_IN(31) xor SHIFT_DATA(31);
--- 80,92 ----
  					else -- ROR #shift_positions
  						SHIFT_DATA <= to_StdLogicVector(to_BitVector(SHIFT_DATA_IN) ror shift_positions);
  						CARRY_OUT  <= SHIFT_DATA_IN(shift_positions - 1);
  					end if;
  
  				when others => -- undefined
! 					SHIFT_DATA <= (others => '-');
  					CARRY_OUT      <= '-';
  			end case;
  			
  			if (STORM_MODE = TRUE) then -- use cool overflow feature
  				if (SHIFT_MODE = S_LSL) then -- overflow detection
  					OVERFLOW_OUT <= SHIFT_DATA_IN(31) xor SHIFT_DATA(31);


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BARREL_SHIFTER

When performin multi cycle memory access operations, the pipeline halt/enable doesnt work properly and only the first cycle is executed.

Example:
Write Rx to the memory and add to the address register Ry an offset afterwards

=> only the memory write is executed

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Storm Core (ARM7 compatible)