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This effectively revertsb380514764andc24473ddff, restoring the state at598cd52272. Before pushing, please check that what you're about to push is sane. Check your local commit log and ensure there isn't anything out-of-place before pushing to mainline. When things like this happen, it wastes everyone's time. I really don't need this in a week when real work™ is busting my balls and I'm behind where I want to be with preparing for MAME release.
117 lines
4.2 KiB
ReStructuredText
117 lines
4.2 KiB
ReStructuredText
The device_memory_interface
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===========================
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1. Capabilities
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---------------
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The device memory interface provides devices with the capability of
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creating address spaces, to which address maps can be associated.
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It's used for any device that provides a (logically) address/data bus
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other devices can be connected to. It's mainly, but not only, cpus.
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The interface allows for an unlimited set of address spaces, numbered
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with small positive values. The IDs should stay small because they
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index vectors to keep the lookup fast. Spaces number 0-3 have an
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associated constant name:
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+----+---------------+
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| ID | Name |
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+====+===============+
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| 0 | AS_PROGRAM |
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+----+---------------+
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| 1 | AS_DATA |
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+----+---------------+
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| 2 | AS_IO |
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+----+---------------+
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| 3 | AS_OPCODES |
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+----+---------------+
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Spaces 0 and 3, e.g. AS_PROGRAM and AS_OPCODE, are special for the
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debugger and some CPUs. AS_PROGRAM is use by the debugger and the
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cpus as the space from with the cpu reads its instructions for the
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disassembler. When present, AS_OPCODE is used by the debugger and
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some cpus to read the opcode part of the instruction. What opcode
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means is device-dependant, for instance for the z80 it's the initial
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byte(s) which are read with the M1 signal asserted. For the 68000 is
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means every instruction word plus the PC-relative accesses. The main,
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but not only, use of AS_OPCODE is to implement hardware decrypting
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instructions separately from the data.
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2. Setup
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--------
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| std::vector<std::pair<int, const address_space_config \*>>\ **memory_space_config**\ (int spacenum) const
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The device must override that method to provide a vector of pairs
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comprising of a space number and its associated
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**address_space_config** describing its configuration. Some examples
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to look up when needed:
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* Standard two-space vector: v60_device
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* Conditional AS_OPCODE: z80_device
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* Inherit config and add a space: m6801_device
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* Inherit config and patch a space: tmpz84c011_device
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| bool **has_configured_map**\ () const
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| bool **has_configured_map**\ (int index) const
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The **has_configured_map** method allows to test in the
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**memory_space_config** method whether an **address_map** has been
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associated with a given space. That allows to implement optional
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memory spaces, such as AS_OPCODES in certain cpu cores. The
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parameterless version tests for space 0.
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3. Associating maps to spaces
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-----------------------------
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Associating maps to spaces is done at the machine config level, after the device declaration.
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| **MCFG_DEVICE_ADDRESS_MAP**\ (_space, _map)
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| **MCFG_DEVICE_PROGRAM_MAP**\ (_map)
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| **MCFG_DEVICE_DATA_MAP**\ (_map)
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| **MCFG_DEVICE_IO_MAP**\ (_map)
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| **MCFG_DEVICE_OPCODES_MAP**\ (_map)
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The generic macro and the four specific ones associate a map to a
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given space. Address maps associated to non-existing spaces are
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ignored (no warning given). devcpu.h defines MCFG_CPU_*_MAP aliases
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to the specific macros.
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| **MCFG_DEVICE_REMOVE_ADDRESS_MAP**\ (_space)
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That macro removes a memory map associated to a given space. Useful
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when removing a map for an optional space in a machine config
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derivative.
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4. Accessing the spaces
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-----------------------
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| address_space &\ **space**\ () const
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| address_space &\ **space**\ (int index) const
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Returns a given address space post-initialization. The parameterless
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version tests for AS_PROGRAM/AS_0. Aborts if the space doesn't exist.
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| bool **has_space**\ () const
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| bool **has_space**\ (int index) const
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Indicates whether a given space actually exists. The parameterless
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version tests for AS_PROGRAM/AS_0.
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5. MMU support for disassembler
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-------------------------------
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| bool **translate**\ (int spacenum, int intention, offs_t &address)
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Does a logical to physical address translation through the device's
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MMU. spacenum gives the space number, intention the type of the
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future access (TRANSLATE_(READ\|WRITE\|FETCH)(\|_USER\|_DEBUG)) and
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address is an inout parameter with the address to translate and its
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translated version. Should return true if the translation went
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correctly, false if the address is unmapped.
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Note that for some historical reason the device itself must override
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the virtual method **memory_translate** with the same signature.
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