mapper

package
v0.27.0 Latest Latest
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 Go to latest Published: Nov 27, 2023 License: GPL-3.0, GPL-3.0 Imports: 2 Imported by: 0

Documentation

Overview

Package mapper contains the CartMapper interface. This interface abstracts the functions required of any cartridge format.

In addition it defines other interfaces that a cartridge mapper may optionally implement for additional functionality for the rest of the emulation. For example, the CartHotspotBus interface can be used to reveal information about the special/hotspot addresses for a cartridge format.

In addition to the interfaces, any additional types are defined. For instance, the CartHotspotInfo type the symbol name and action type for a every hotspot in the cartridge.

Index

Constants

View Source 
const CartDrivenPins = 0xff

CartDrivenPins is included for clarity. In the vast majority of cases a cartridge mapper will drive all pins on the data bus during access. Use CartDrivenPins rather than 0xff.

In the case where the data bus pins are not driven a 0 will suffice.

For any cases where the databus is partially driven, the appropriate value can be used.

Variables

This section is empty.

Functions

This section is empty.

Types

type BankContent 

type BankContent struct {
	// bank number
	Number int

	// copy of the bank data
	Data []uint8

	// the segment origins that this data is allowed to be mapped to. most
	// cartridges will have one entry. values in the array will refer to
	// addresses in the cartridge address space. by convention the mappers will
	// refer to the primary mirror.
	//
	//	memorymap.OriginCart <= origins[n] <= memorymap.MemtopCart
	//
	// to index the Data field, transform the origin and any address derived
	// from it, with memorymap.CartridgeBits
	//
	//	idx := Origins[0] & memorymap.CartridgeBits
	//	v := Data[idx]
	//
	// address values are supplied by the mapper implementation and must be
	// cartridge addresses and should in the primary cartridge mirror range
	// (ie. 0x1000 to 0x1fff)j
	Origins []uint16
}

BankContent contains data and ID of a cartridge bank. Used by CopyBanks() and helps the disassembly process.

type BankInfo 

type BankInfo struct {
	// bank number
	Number int

	// name of bank. used for special purpose banks (eg. supercharger BIOS).
	// should be empty if bank has no name.
	Name string

	// is cartridge memory segmented and if so which segment is this bank
	// mapped to
	IsSegmented bool
	Segment     int

	// is cartridge bank writable
	IsRAM bool

	// if the address used to generate the Details is not a cartridge address.
	// this happens deliberately for example, during the Supercharger load
	// procedure, where execution happens (briefly) inside the main VCS RAM
	NonCart bool

	// the cartridge is currently feeding NOP bytes onto the data bus and
	// therefore the data from this bank should not be considered predictable.
	//
	// this flag has been added to support the ARM coprocessor found in
	// conjunction with CDF* and DPC+ mappers. future coprocessors may work
	// differently.
	ExecutingCoprocessor bool

	// if ExecutingCoprocessor is valid then we also record the address the
	// processor will resume from.
	CoprocessorResumeAddr uint16
}

BankInfo is used to identify a cartridge bank. In some instance a bank can be identified by it's bank number only. In other contexts more detail is required and so BankInfo is used isntead.

func (BankInfo) String 

func (b BankInfo) String() string

very basic String representation of BankInfo.

type CartBusStuff added in v0.19.3 

type CartBusStuff interface {
	BusStuff() (uint8, bool)
}

CartBusStuff is implemented by cartridge mappers than can arbitrarily drive the pins on the data bus during a write.

type CartContainer 

type CartContainer interface {
	CartMapper
	ContainerID() string
}

CartContainer is a special CartMapper type that wraps another CartMapper. For example, the PlusROM type.

type CartHotLoader added in v0.12.1 

type CartHotLoader interface {
	HotLoad([]byte) error
}

CartHotLoader is implemented by cartridge mappers that can be hot-loaded. ie. ROM data updated but keeping RAM memory intact.

type CartHotspotAction 

type CartHotspotAction int

CartHotspotAction defines the action of a hotspot address. 

const (
	// the most common type of hotspot is the bankswitch. for these hotspots
	// the bank/segment is switched when the address is read/write.
	HotspotBankSwitch CartHotspotAction = iota

	// some cartridge mappers have additional registers.
	HotspotRegister

	// a function is a catch all category that describes any hotspot address
	// that has some other than or more complex than just bank switching. for
	// example, the Supercharger CONFIG address causes bank-switching to take
	// place but is none-the-less defined as a HotspotFunction.
	HotspotFunction

	// some hotspots will be defined but be unused or reserved by the
	// cartridge.
	HotspotReserved
)

List of valid CartHotspotActions.

type CartHotspotInfo 

type CartHotspotInfo struct {
	Symbol string
	Action CartHotspotAction
}

HotspotInfo details the name and purpose of hotspot address.

type CartHotspotsBus 

type CartHotspotsBus interface {
	ReadHotspots() map[uint16]CartHotspotInfo
	WriteHotspots() map[uint16]CartHotspotInfo
}

CartHotspotsBus will be implemented for cartridge mappers that want to report details of any special addresses. We'll call these hotspots for all types of special addresses, not just bank switches.

The index to the returned maps, must be addresses in the cartridge address range. For normality, this should be in the primary cartridge mirror (ie. 0x1000 to 0x1fff).

type CartLabels added in v0.17.0 

type CartLabels map[uint16]string

CartLabels is returned by CartLabelsBus. Maps addresses to symbols. Address can be any address, not just those in the cartridge.

Currently, addresses are specific and should not be mirrored.

type CartLabelsBus added in v0.17.0 

type CartLabelsBus interface {
	Labels() CartLabels
}

CartLabelsBus will be implemented for cartridge mappers that want to report any special labels for the cartridge type.

type CartMapper 

type CartMapper interface {
	MappedBanks() string
	ID() string

	Snapshot() CartMapper
	Plumb(*environment.Environment)

	// reset volatile areas of the cartridge. for many cartridge mappers this
	// will do nothing but those with registers or ram should perform an
	// explicit reset (possibly with randomisation)
	Reset()

	// access the cartridge at the specified address. the cartridge is expected to
	// drive the data bus and so this can be thought of as a "read" operation
	//
	// the mask return value allows the mapper to identify which data pins
	// which are being driven by the cartridge. in most cases, the mask should
	// be the CartDrivenPins value
	//
	// the address parameter should be normalised. ie. no mirror information
	Access(addr uint16, peek bool) (data uint8, mask uint8, err error)

	// access the cartridge at the specified volatile address. if the location
	// at that address is not volatile, the data value can be ignored
	//
	// we can think of this as a write operation but it will be called during a
	// read operation too. this is because the cartidge cannot distinguish read
	// and write operations and any access of a volatile address will affect it
	//
	// the address parameter should be normalised. ie. no mirror information
	AccessVolatile(addr uint16, data uint8, poke bool) error

	NumBanks() int
	GetBank(addr uint16) BankInfo

	// AccessPassive is called so that the cartridge can respond to changes to the
	// address and data bus even when the data bus is not addressed to the cartridge.
	//
	// see the commentary for the AccessPassive() function in the Cartridge type
	// for an explanation for why this is needed
	AccessPassive(addr uint16, data uint8) error

	// some cartridge mappings have independent clocks that tick and change
	// internal cartridge state. the step() function is called every cpu cycle
	// at the rate specified.
	Step(clock float32)

	// return copies of all banks in the cartridge. the disassembly process
	// uses this to access cartridge data freely and without affecting the
	// state of the cartridge.
	CopyBanks() []BankContent
}

CartMapper implementations hold the actual data from the loaded ROM and keeps track of which banks are mapped to individual addresses. for convenience, functions with an address argument receive that address normalised to a range of 0x0000 to 0x0fff.

type CartPatchable added in v0.27.0 

type CartPatchable interface {
	// patch is different to poke in that it alters the data as though it was
	// being read from disk. that is, the offset is measured from the start of
	// the file. the cartmapper must translate the offset and update the correct
	// data structure as appropriate.
	Patch(offset int, data uint8) error
}

CartPatchable is implemented by cartridge mappers than can have their binary patched as part of the load process

type CartRAM 

type CartRAM struct {
	Label  string
	Origin uint16
	Data   []uint8
	Mapped bool
}

CartRAM represents a single segment of RAM in the cartridge. A cartridge may contain more than one segment of RAM. The Label field can help distinguish between the different segments.

The Origin field specifies the address of the lowest byte in RAM. The Data field is a copy of the actual bytes in the cartidge RAM. Because Cartidge is addressable, it is also possible to update cartridge RAM through the normal memory buses; although in the context of a debugger it is probably more convience to use PutRAM() in the CartRAMbus interface.

type CartRAMbus 

type CartRAMbus interface {
	GetRAM() []CartRAM

	// Update the value at the index of the specified RAM bank. Note that this
	// is not the address; it refers to the Data array as returned by GetRAM()
	PutRAM(bank int, idx int, data uint8)
}

CartRAMbus is implemented for catridge mappers that have an addressable RAM area. This differs from a Static area which is not addressable by the VCS.

Note that for convenience, some mappers will implement this interface but have no RAM for the specific cartridge. In these case GetRAM() will return nil.

The test for whether a specific cartridge has additional RAM should include a interface type asserstion as well as checking GetRAM() == nil.

type CartROMDump added in v0.19.3 

type CartROMDump interface {
	ROMDump(filename string) error
}

CartROMDump is implemented by cartridge mappers that can save themselves to disk.

type CartRegisters 

type CartRegisters interface {
	String() string
}

CartRegisters conceptualises the cartridge specific registers that are inaccessible through normal addressing.

type CartRegistersBus 

type CartRegistersBus interface {
	// GetRegisters returns a copy of the cartridge's registers
	GetRegisters() CartRegisters

	// Update a register in the cartridge with new data.
	//
	// Depending on the complexity of the cartridge, the register argument may
	// need to be a structured string to uniquely identify a register (eg. a
	// JSON string, although that's probably going over the top). The details
	// of what is valid should be specified in the documentation of the mappers
	// that use the CartRegistersbus.
	//
	// The data string will be converted to whatever type is required for the
	// register. For simple types then this will be usual Go representation,
	// (eg. true of false for boolean types) but it may be a more complex
	// representation. Again, the details of what is valid should be specified
	// in the mapper documentation.
	PutRegister(register string, data string)
}

CartRegistersBus defines the operations required for a debugger to access any coprocessor in a cartridge.

The mapper is allowed to panic if it is not interfaced with correctly.

You should know the precise cartridge mapper for the CartRegisters to be usable.

So what's the point of the interface if you need to know the details of the underlying type? Couldn't we just use a type assertion?

Yes, but doing it this way helps with the lazy evaluation system used by debugging GUIs. The point of the lazy system is to prevent race conditions and the way we do that is to make copies of system variables before using it in the GUI. Now, because we must know the internals of the cartridge format, could we not just make those copies manually? Again, yes. But that would mean another place where the cartridge's internal knowledge needs to be coded (we need to use that knowledge in the GUI code but it would be nice to avoid it in the lazy system).

The GetRegisters() allows us to conceptualise the copying process and to keep the details inside the cartridge implementation as much as possible.

type CartRewindBoundary 

type CartRewindBoundary interface {
	RewindBoundary() bool
}

CartRewindBoundary is implemented by cartridge mappers that require special handling from the rewind system. For some cartridge types it is not appropriate to allow rewind history to survive past a certain point.

type CartStatic 

type CartStatic interface {
	// returns a list of memory areas in the cartridge's static memory
	Segments() []CartStaticSegment

	// returns a copy of the data in the named segment. the segment name should
	// be taken from the Name field of one of the CartStaticSegment instances
	// returned by the Segments() function
	Reference(segment string) ([]uint8, bool)

	// read 8, 16 or 32 bit values from the address. the address should be in
	// the range given in one of the CartStaticSegment returned by the
	// Segments() function.
	Read8bit(addr uint32) (uint8, bool)
	Read16bit(addr uint32) (uint16, bool)
	Read32bit(addr uint32) (uint32, bool)
}

CartStatic conceptualises a static data area that is inaccessible through the 6507.

type CartStaticBus 

type CartStaticBus interface {
	// GetStatic returns a copy of the cartridge's static areas
	GetStatic() CartStatic

	// Update the value at the index of the specified segment. the segment
	// argument should come from the Name field of the CartStaticSegment type
	// returned by CartStatic.Segments()
	//
	// The idx field should count from 0 and be no higher than the size of
	// memory in the segment (the differenc of Memtop and Origin returned in
	// the CartStaticSegment type).
	//
	// Returns false if segment is unknown or idx is out of range.
	//
	// PutStatic() will be working on the original data so PutStatic should be run
	// in the same goroutine as the main emulation.
	PutStatic(segment string, idx int, data uint8) bool
}

CartStaticBus defines the operations required for a debugger to access the static memory of a cartridge.

Static memory is so called because it is inaccessible from the 6507 program. From that point of view the memory is static and can't be changed. It may however be changed by any coprocessor on the cartridge.

(Historically, the StaticBus and related types were added to support the DPC mapper type, where the memory indeed never can change. When the later cartridge mappers, DPC+ and CDF, were added the name stuck).

type CartStaticSegment added in v0.18.0 

type CartStaticSegment struct {
	Name   string
	Origin uint32
	Memtop uint32
}

CartStaticSegment describes a single region of the underlying CartStatic memory. The Name field can be used to reference the actual memory or to update the underlying memory with CartStaticBus.PutStatic()

type CartTapeBus 

type CartTapeBus interface {
	// Move tape loading to the beginning of the tape
	Rewind()

	// Set tape counter to specified value
	SetTapeCounter(c int)

	// GetTapeState retrieves a copy of the current state of the tape. returns
	// true is state is valid
	GetTapeState() (bool, CartTapeState)
}

CartTapeBus defines additional debugging functions for cartridge types that use tapes.

type CartTapeState 

type CartTapeState struct {
	Counter    int
	MaxCounter int
	Time       float64
	MaxTime    float64
	Data       []float32
}

CartTapeState is the current state of the tape.

type OptionalSuperchip 

type OptionalSuperchip interface {
	// the force argument causes the superchip to be added whether it needs it or not
	AddSuperchip(force bool)
}

OptionalSuperchip are implemented by CartMapper implementations that require an optional superchip. This shouldn't be used to decide if a cartridge has additional RAM or not. Use the CartRAMbus interface for that.

type PlumbFromDifferentEmulation added in v0.15.0 

type PlumbFromDifferentEmulation interface {
	PlumbFromDifferentEmulation(*environment.Environment)
}

PlumbFromDifferentEmulation is for mappers that are sensitive to being transferred from one emulation to another.

When state is being plumbed into a different emulation to the one that has been created then this interface should be used when available, instead of the normal Plumb().

Source Files

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