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[/] [single_port/] [trunk/] [VHDL/] [single_port.vhd] - Rev 2
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-- $Author: rpaley_yid $ -- $Date: 2003-01-14 21:48:11 $ -- $Header: /home/marcus/revision_ctrl_test/oc_cvs/cvs/single_port/VHDL/single_port.vhd,v 1.1.1.1 2003-01-14 21:48:11 rpaley_yid Exp $ -- $Locker -- $Revision: 1.1.1.1 $ -- $State: Exp $ -- -------------------------------------------------------------------------- -- -- Purpose: This is a single port asynchronous memory. This files -- describes three architectures. Two architectures are traditional -- array based memories. One describes the memory as an array of -- STD_LOGIC_VECTOR, and the other describes the ARRAY as BIT_VECTOR. -- The third architecture describes the memory arranged as a linked -- list in order to conserve computer memory usage. The memory -- is organized as a linked list of BIT_VECTOR arrays whose size -- is defined PAGEDEPTH in single_port_pkg.vhd. -- -- -- References: -- 1. The Designer's Guide to VHDL by Peter Ashenden -- ISBN: 1-55860-270-4 (pbk.) -- 2. Writing Testbenches - Functional Verification of HDL models by -- Janick Bergeron | ISBN: 0-7923-7766-4 -- -- Notes: -- -- -------------------------------------------------------------------------- LIBRARY IEEE; LIBRARY WORK; USE IEEE.STD_LOGIC_1164.ALL; USE IEEE.NUMERIC_STD.ALL; USE WORK.single_port_pkg.ALL; USE WORK.linked_list_mem_pkg.ALL; ENTITY single_port IS GENERIC ( rnwtQ : TIME := 1 NS ); PORT ( d : IN data_inter_typ; q : OUT data_inter_typ; a : IN addr_inter_typ; rnw : IN STD_LOGIC; dealloc_mem : IN BOOLEAN ); END ENTITY single_port; ARCHITECTURE ArrayMemNoFlag OF single_port IS BEGIN mem_proc : PROCESS TYPE mem_typ IS ARRAY ( 0 TO PAGENUM*PAGEDEPTH-1) OF data_inter_typ; VARIABLE mem : mem_typ; BEGIN WAIT on rnw'transaction; IF ( rnw = '0') THEN -- Write mem(TO_INTEGER(unsigned(a))) := d; ELSE -- Read q <= mem(TO_INTEGER(unsigned(a))) AFTER rnwtQ; END IF; END PROCESS mem_proc; END ArrayMemNoFlag; ARCHITECTURE ArrayMem OF single_port IS BEGIN mem_proc : PROCESS TYPE mem_typ IS ARRAY ( 0 TO PAGENUM*PAGEDEPTH-1 ) OF data_typ; TYPE flag_typ IS ARRAY ( 0 TO PAGENUM*PAGEDEPTH-1 ) OF BOOLEAN; VARIABLE mem : mem_typ; VARIABLE flag : flag_typ; BEGIN WAIT ON rnw'transaction; IF ( rnw = '0') THEN -- Write mem(TO_INTEGER(unsigned(a))) := TO_BITVECTOR(d); flag(TO_INTEGER(unsigned(a))) := true; -- set valid memory location flag ELSE -- read data, either valid or 'U' IF ( flag(TO_INTEGER(unsigned(a))) = true ) THEN q <= TO_STDLOGICVECTOR(mem(TO_INTEGER(unsigned(a)))) AFTER rnwtQ; ELSE -- reading invalid memory location q <= (OTHERS => 'U') after rnwtQ; END IF; END IF; END PROCESS mem_proc; END ArrayMem; ARCHITECTURE LinkedList OF single_port IS BEGIN mem_proc : PROCESS VARIABLE mem_page_v : mem_page_ptr; VARIABLE d_v : data_inter_typ; VARIABLE a_v : addr_typ; VARIABLE WRITE_MEM_v : BOOLEAN := true; VARIABLE READ_MEM_v : BOOLEAN := false; BEGIN WAIT ON dealloc_mem'transaction , rnw'TRANSACTION; IF NOT dealloc_mem THEN d_v := d; a_v := TO_INTEGER(unsigned(a)); IF ( rnw = '0' ) THEN -- write to linked list memory rw_mem( data => d_v, addr => a_v, write_flag => WRITE_MEM_v, next_cell => mem_page_v ); ELSE -- read from linked list memory rw_mem( data => d_v, addr => a_v, write_flag => READ_MEM_v, next_cell => mem_page_v ); q <= d_v after rnwtQ; END IF; ELSE -- Deallocate memory from work station memory. deallocate_mem(mem_page_v); END IF; END PROCESS mem_proc; END LinkedList; -- $Log: not supported by cvs2svn $ -- Revision 1.1 2003/01/14 17:48:31 Default -- Initial revision -- -- Revision 1.1 2002/12/24 18:09:05 Default -- Initial revision --
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