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///////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//
//
// Filename:    cpudefs.v
// Filename:    cpudefs.v
//
//
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
//
//
// Purpose:     Some architectures have some needs, others have other needs.
// Purpose:     Some architectures have some needs, others have other needs.
//              Some of my projects need a Zip CPU with pipelining, others
//              Some of my projects need a Zip CPU with pipelining, others
//      can't handle the timing required to get the answer from the ALU
//      can't handle the timing required to get the answer from the ALU
//      back into the input for the ALU.  As each different projects has
//      back into the input for the ALU.  As each different projects has
//      different needs, I can either 1) reconfigure my entire baseline prior
//      different needs, I can either 1) reconfigure my entire baseline prior
//      to building each project, or 2) host a configuration file which contains
//      to building each project, or 2) host a configuration file which contains
//      the information regarding each baseline.  This file is that
//      the information regarding each baseline.  This file is that
//      configuration file.  It controls how the CPU (not the system,
//      configuration file.  It controls how the CPU (not the system,
//      peripherals, or other) is defined and implemented.  Several options
//      peripherals, or other) is defined and implemented.  Several options
//      are available within here, making the Zip CPU pipelined or not,
//      are available within here, making the Zip CPU pipelined or not,
//      able to handle a faster clock with more stalls or a slower clock with
//      able to handle a faster clock with more stalls or a slower clock with
//      no stalls, etc.
//      no stalls, etc.
//
//
//      This file encapsulates those control options.
//      This file encapsulates those control options.
//
//
//      The number of LUTs the Zip CPU uses varies dramatically with the
//      The number of LUTs the Zip CPU uses varies dramatically with the
//      options defined in this file.
//      options defined in this file.
//
//
//
//
// Creator:     Dan Gisselquist, Ph.D.
// Creator:     Dan Gisselquist, Ph.D.
//              Gisselquist Technology, LLC
//              Gisselquist Technology, LLC
//
//
///////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
//
//
// Copyright (C) 2015-2016, Gisselquist Technology, LLC
// Copyright (C) 2015-2016, Gisselquist Technology, LLC
//
//
// This program is free software (firmware): you can redistribute it and/or
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of  the GNU General Public License as published
// modify it under the terms of  the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
// your option) any later version.
//
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
// for more details.
//
//
 
// You should have received a copy of the GNU General Public License along
 
// with this program.  (It's in the $(ROOT)/doc directory.  Run make with no
 
// target there if the PDF file isn't present.)  If not, see
 
// <http://www.gnu.org/licenses/> for a copy.
 
//
// License:     GPL, v3, as defined and found on www.gnu.org,
// License:     GPL, v3, as defined and found on www.gnu.org,
//              http://www.gnu.org/licenses/gpl.html
//              http://www.gnu.org/licenses/gpl.html
//
//
//
//
///////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
 
//
 
//
`ifndef CPUDEFS_H
`ifndef CPUDEFS_H
`define CPUDEFS_H
`define CPUDEFS_H
//
//
//
//
// The first couple options control the Zip CPU instruction set, and how
// The first couple options control the Zip CPU instruction set, and how
// it handles various instructions within the set:
// it handles various instructions within the set:
//
//
//
//
// OPT_ILLEGAL_INSTRUCTION is part of a new section of code that is supposed
// OPT_ILLEGAL_INSTRUCTION is part of a new section of code that is supposed
// to recognize illegal instructions and interrupt the CPU whenever one such
// to recognize illegal instructions and interrupt the CPU whenever one such
// instruction is encountered.  The goal is to create a soft floating point
// instruction is encountered.  The goal is to create a soft floating point
// unit via this approach, that can then be replaced with a true floating point
// unit via this approach, that can then be replaced with a true floating point
// unit.  As I'm not there yet, it just catches illegal instructions and
// unit.  As I'm not there yet, it just catches illegal instructions and
// interrupts the CPU on any such instruction--when defined.  Otherwise,
// interrupts the CPU on any such instruction--when defined.  Otherwise,
// illegal instructions are quietly ignored and their behaviour is ...
// illegal instructions are quietly ignored and their behaviour is ...
// undefined. (Many get treated like NOOPs ...)
// undefined. (Many get treated like NOOPs ...)
//
//
// I recommend setting this flag so highly, that I'm likely going to remove
// I recommend setting this flag so highly, that I'm likely going to remove
// the option to turn this off in future versions of this CPU.
// the option to turn this off in future versions of this CPU.
//
//
`define OPT_ILLEGAL_INSTRUCTION
`define OPT_ILLEGAL_INSTRUCTION
//
//
//
//
//
//
// OPT_MULTIPLY controls whether or not the multiply is built and included
// OPT_MULTIPLY controls whether or not the multiply is built and included
// in the ALU by default.  Set this option and a parameter will be set that
// in the ALU by default.  Set this option and a parameter will be set that
// includes the multiply.  (This parameter may still be overridden, as with
// includes the multiply.  (This parameter may still be overridden, as with
// any parameter ...)  If the multiply is not included and
// any parameter ...)  If the multiply is not included and
// OPT_ILLEGAL_INSTRUCTION is set, then the multiply will create an illegal
// OPT_ILLEGAL_INSTRUCTION is set, then the multiply will create an illegal
// instruction that will then trip the illegal instruction trap.
// instruction that will then trip the illegal instruction trap.
//
//
// Either not defining this value, or defining it to zero will disable the
// Either not defining this value, or defining it to zero will disable the
// hardware multiply.  A value of '1' will cause the multiply to occurr in one
// hardware multiply.  A value of '1' will cause the multiply to occurr in one
// clock cycle only--often at the expense of the rest of the CPUs speed.
// clock cycle only--often at the expense of the rest of the CPUs speed.
// A value of 2 will cause the multiply to have a single delay cycle, 3 will
// A value of 2 will cause the multiply to have a single delay cycle, 3 will
// have two delay cycles, and 4 (or more) will have 3 delay cycles.
// have two delay cycles, and 4 (or more) will have 3 delay cycles.
//
//
//
//
`define OPT_MULTIPLY    3
`define OPT_MULTIPLY    3
//
//
//
//
//
//
// OPT_DIVIDE controls whether or not the divide instruction is built and
// OPT_DIVIDE controls whether or not the divide instruction is built and
// included into the ZipCPU by default.  Set this option and a parameter will
// included into the ZipCPU by default.  Set this option and a parameter will
// be set that causes the divide unit to be included.  (This parameter may
// be set that causes the divide unit to be included.  (This parameter may
// still be overridden, as with any parameter ...)  If the divide is not
// still be overridden, as with any parameter ...)  If the divide is not
// included and OPT_ILLEGAL_INSTRUCTION is set, then the multiply will create
// included and OPT_ILLEGAL_INSTRUCTION is set, then the multiply will create
// an illegal instruction exception that will send the CPU into supervisor
// an illegal instruction exception that will send the CPU into supervisor
// mode.
// mode.
//
//
//
//
`define OPT_DIVIDE
`define OPT_DIVIDE
//
//
//
//
//
//
// OPT_IMPLEMENT_FPU will (one day) control whether or not the floating point
// OPT_IMPLEMENT_FPU will (one day) control whether or not the floating point
// unit (once I have one) is built and included into the ZipCPU by default. 
// unit (once I have one) is built and included into the ZipCPU by default.
// At that time, if this option is set then a parameter will be set that
// At that time, if this option is set then a parameter will be set that
// causes the floating point unit to be included.  (This parameter may
// causes the floating point unit to be included.  (This parameter may
// still be overridden, as with any parameter ...)  If the floating point unit
// still be overridden, as with any parameter ...)  If the floating point unit
// is not included and OPT_ILLEGAL_INSTRUCTION is set, then as with the
// is not included and OPT_ILLEGAL_INSTRUCTION is set, then as with the
// multiply and divide any floating point instruction will result in an illegal
// multiply and divide any floating point instruction will result in an illegal
// instruction exception that will send the CPU into supervisor mode.
// instruction exception that will send the CPU into supervisor mode.
//
//
//
//
// `define      OPT_IMPLEMENT_FPU
// `define      OPT_IMPLEMENT_FPU
//
//
//
//
//
//
// OPT_NEW_INSTRUCTION_SET controls whether or not the new instruction set
 
// is in use.  The new instruction set contains space for floating point
 
// operations, signed and unsigned divide instructions, as well as bit reversal
 
// and ... at least two other operations yet to be defined.  The decoder alone
 
// uses about 70 fewer LUTs, although in practice this works out to 12 fewer
 
// when all works out in the wash.  Further, floating point and divide
 
// instructions will cause an illegal instruction exception if they are not
 
// implemented--so software capability can be built to use these instructions
 
// immediately, even if the hardware is not yet ready.
 
//
 
// This option is likely to go away in the future, obsoleting the previous
 
// instruction set, so I recommend setting this option and switching to the
 
// new instruction set as soon as possible.
 
//
 
`define OPT_NEW_INSTRUCTION_SET
 
//
 
//
 
//
 
//
 
//
 
//
//
// OPT_SINGLE_FETCH controls whether or not the prefetch has a cache, and 
// OPT_SINGLE_FETCH controls whether or not the prefetch has a cache, and
// whether or not it can issue one instruction per clock.  When set, the
// whether or not it can issue one instruction per clock.  When set, the
// prefetch has no cache, and only one instruction is fetched at a time.
// prefetch has no cache, and only one instruction is fetched at a time.
// This effectively sets the CPU so that only one instruction is ever 
// This effectively sets the CPU so that only one instruction is ever
// in the pipeline at once, and hence you may think of this as a "kill 
// in the pipeline at once, and hence you may think of this as a "kill
// pipeline" option.  However, since the pipelined fetch component uses so
// pipeline" option.  However, since the pipelined fetch component uses so
// much area on the FPGA, this is an important option to use in trimming down
// much area on the FPGA, this is an important option to use in trimming down
// used area if necessary.  Hence, it needs to be maintained for that purpose.
// used area if necessary.  Hence, it needs to be maintained for that purpose.
// Be aware, though, it will drop your performance by a factor between 2x and
// Be aware, though, it will drop your performance by a factor between 2x and
// 3x.
// 3x.
//
//
// We can either pipeline our fetches, or issue one fetch at a time.  Pipelined
// We can either pipeline our fetches, or issue one fetch at a time.  Pipelined
// fetches are more complicated and therefore use more FPGA resources, while
// fetches are more complicated and therefore use more FPGA resources, while
// single fetches will cause the CPU to stall for about 5 stalls each 
// single fetches will cause the CPU to stall for about 5 stalls each
// instruction cycle, effectively reducing the instruction count per clock to
// instruction cycle, effectively reducing the instruction count per clock to
// about 0.2.  However, the area cost may be worth it.  Consider:
// about 0.2.  However, the area cost may be worth it.  Consider:
//
//
//      Slice LUTs              ZipSystem       ZipCPU
//      Slice LUTs              ZipSystem       ZipCPU
//      Single Fetching         2521            1734
//      Single Fetching         2521            1734
//      Pipelined fetching      2796            2046
//      Pipelined fetching      2796            2046
//      (These numbers may be dated, but should still be representative ...)
//      (These numbers may be dated, but should still be representative ...)
//
//
// I recommend only defining this if you "need" to, if area is tight and
// I recommend only defining this if you "need" to, if area is tight and
// speed isn't as important.  Otherwise, just leave this undefined.
// speed isn't as important.  Otherwise, just leave this undefined.
//
//
// `define      OPT_SINGLE_FETCH
// `define      OPT_SINGLE_FETCH
//
//
//
//
//
//
// The next several options are pipeline optimization options.  They make no
// The next several options are pipeline optimization options.  They make no
// sense in a single instruction fetch mode, hence we #ifndef them so they
// sense in a single instruction fetch mode, hence we #ifndef them so they
// are only defined if we are in a full pipelined mode (i.e. OPT_SINGLE_FETCH
// are only defined if we are in a full pipelined mode (i.e. OPT_SINGLE_FETCH
// is not defined).
// is not defined).
//
//
`ifndef OPT_SINGLE_FETCH
`ifndef OPT_SINGLE_FETCH
//
//
//
//
//
//
// OPT_PIPELINED is the natural result and opposite of using the single 
// OPT_PIPELINED is the natural result and opposite of using the single
// instruction fetch unit.  If you are not using that unit, the ZipCPU will
// instruction fetch unit.  If you are not using that unit, the ZipCPU will
// be pipelined.  The option is defined here more for readability than 
// be pipelined.  The option is defined here more for readability than
// anything else, since OPT_PIPELINED makes more sense than OPT_SINGLE_FETCH,
// anything else, since OPT_PIPELINED makes more sense than OPT_SINGLE_FETCH,
// well ... that and it does a better job of explaining what is going on.
// well ... that and it does a better job of explaining what is going on.
//
//
// In other words, leave this define alone--lest you break the ZipCPU.
// In other words, leave this define alone--lest you break the ZipCPU.
//
//
`define OPT_PIPELINED
`define OPT_PIPELINED
//
//
//
//
//
//
// OPT_TRADITIONAL_PFCACHE allows you to switch between one of two prefetch
// OPT_TRADITIONAL_PFCACHE allows you to switch between one of two prefetch
// caches.  If enabled, a more traditional cache is implemented.  This more
// caches.  If enabled, a more traditional cache is implemented.  This more
// traditional cache (currently) uses many more LUTs, but it also reduces
// traditional cache (currently) uses many more LUTs, but it also reduces
// the stall count tremendously over the alternative hacked pipeline cache.
// the stall count tremendously over the alternative hacked pipeline cache.
// (The traditional pfcache is also pipelined, whereas the pipeline cache
// (The traditional pfcache is also pipelined, whereas the pipeline cache
// implements a windowed approach to caching.)
// implements a windowed approach to caching.)
//
//
// If you have the fabric to support this option, I recommend including it.
// If you have the fabric to support this option, I recommend including it.
//
//
`define OPT_TRADITIONAL_PFCACHE
`define OPT_TRADITIONAL_PFCACHE
//
//
//
//
//
//
// OPT_EARLY_BRANCHING is an attempt to execute a BRA statement as early
// OPT_EARLY_BRANCHING is an attempt to execute a BRA statement as early
// as possible, to avoid as many pipeline stalls on a branch as possible.
// as possible, to avoid as many pipeline stalls on a branch as possible.
// It's not tremendously successful yet--BRA's still suffer stalls,
// It's not tremendously successful yet--BRA's still suffer stalls,
// but I intend to keep working on this approach until the number of stalls
// but I intend to keep working on this approach until the number of stalls
// gets down to one or (ideally) zero.  (With the OPT_TRADITIONAL_PFCACHE, this
// gets down to one or (ideally) zero.  (With the OPT_TRADITIONAL_PFCACHE, this
// gets down to a single stall cycle ...)  That way a "BRA" can be used as the
// gets down to a single stall cycle ...)  That way a "BRA" can be used as the
// compiler's branch prediction optimizer: BRA's barely stall, while branches
// compiler's branch prediction optimizer: BRA's barely stall, while branches
// on conditions will always suffer about 4 stall cycles or so.
// on conditions will always suffer about 4 stall cycles or so.
//
//
// I recommend setting this flag, so as to turn early branching on.
// I recommend setting this flag, so as to turn early branching on.
//
//
`define OPT_EARLY_BRANCHING
`define OPT_EARLY_BRANCHING
//
//
//
//
//
//
// OPT_PIPELINED_BUS_ACCESS controls whether or not LOD/STO instructions
// OPT_PIPELINED_BUS_ACCESS controls whether or not LOD/STO instructions
// can take advantaged of pipelined bus instructions.  To be eligible, the
// can take advantaged of pipelined bus instructions.  To be eligible, the
// operations must be identical (cannot pipeline loads and stores, just loads
// operations must be identical (cannot pipeline loads and stores, just loads
// only or stores only), and the addresses must either be identical or one up
// only or stores only), and the addresses must either be identical or one up
// from the previous address.  Further, the load/store string must all have
// from the previous address.  Further, the load/store string must all have
// the same conditional.  This approach gains the must use, in my humble
// the same conditional.  This approach gains the must use, in my humble
// opinion, when saving registers to or restoring registers from the stack
// opinion, when saving registers to or restoring registers from the stack
// at the beginning/end of a procedure, or when doing a context swap.
// at the beginning/end of a procedure, or when doing a context swap.
//
//
// I recommend setting this flag, for performance reasons, especially if your
// I recommend setting this flag, for performance reasons, especially if your
// wishbone bus can handle pipelined bus accesses.
// wishbone bus can handle pipelined bus accesses.
//
//
`define OPT_PIPELINED_BUS_ACCESS
`define OPT_PIPELINED_BUS_ACCESS
//
//
//
//
//
//
`ifdef  OPT_NEW_INSTRUCTION_SET
 
//
//
//
//
//
// The instruction set defines an optional compressed instruction set (CIS)
// The new instruction set also defines a set of very long instruction words.
// complement.  These were at one time erroneously called Very Long Instruction
// Well, calling them "very long" instruction words is probably a misnomer,
// Words.  They are more appropriately referred to as compressed instructions.
// although we're going to do it.  They're really 2x16-bit instructions---
// The compressed instruction format allows two instructions to be packed into
// instruction words that pack two instructions into one word.  (2x14 bit
// the same instruction word.  Some instructions can be compressed, not all.
// really--'cause you need a bit to note the instruction is a 2x instruction,
// Compressed instructions take the same time to complete.  Set OPT_CIS to
// and then 3-bits for the condition codes ...)  Set OPT_VLIW to include these
// include these double instructions as part of the instruction set.  These
// double instructions as part of the new instruction set.  These allow a single
// instructions are designed to get more code density from the instruction set,
// instruction to contain two instructions within.   These instructions are
// and to hopefully take some pain off of the performance of the pre-fetch and
// designed to get more code density from the instruction set, and to hopefully
// instruction cache.
// take some pain off of the performance of the pre-fetch and instruction cache.
 
//
//
// These new instructions, however, also necessitate a change in the Zip
// These new instructions, however, also necessitate a change in the Zip
// CPU--the Zip CPU can no longer execute instructions atomically.  It must
// CPU--the Zip CPU can no longer execute instructions atomically.  It must
// now execute non-VLIW instructions, or VLIW instruction pairs, atomically. 
// now execute non-CIS instructions, or CIS instruction pairs, atomically. 
// This logic has been added into the ZipCPU, but it has not (yet) been
// This logic has been added into the ZipCPU, but it has not (yet) been
// tested thoroughly.
// tested thoroughly.
//
//
// Oh, and the assembler, the debugger, and the object file dumper, and the
 
// simulator all need to be updated as well ....
 
//
 
`define OPT_VLIW
 
//
//
 
`define OPT_CIS
//
//
`endif // OPT_NEW_INSTRUCTION_SET
 
//
//
//
//
`endif  // OPT_SINGLE_FETCH
`endif  // OPT_SINGLE_FETCH
//
//
//
//
//
//
// Now let's talk about peripherals for a moment.  These next two defines
// Now let's talk about peripherals for a moment.  These next two defines
// control whether the DMA controller is included in the Zip System, and
// control whether the DMA controller is included in the Zip System, and
// whether or not the 8 accounting timers are also included.  Set these to
// whether or not the 8 accounting timers are also included.  Set these to
// include the respective peripherals, comment them out not to.
// include the respective peripherals, comment them out not to.
//
//
`define INCLUDE_DMA_CONTROLLER
`define INCLUDE_DMA_CONTROLLER
`define INCLUDE_ACCOUNTING_COUNTERS
`define INCLUDE_ACCOUNTING_COUNTERS
//
//
//
//
// `define      DEBUG_SCOPE
// `define      DEBUG_SCOPE
//
//
`endif  // CPUDEFS_H
`endif  // CPUDEFS_H
 
 

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