+@section ARC Architecture
+@cindex ARC
+
+Synopsys DesignWare ARC Processors are a family of 32-bit CPUs that SoC
+designers can optimize for a wide range of uses, from deeply embedded to
+high-performance host applications in a variety of market segments. See more
+at: @url{http://www.synopsys.com/IP/ProcessorIP/ARCProcessors/Pages/default.aspx}.
+OpenOCD currently supports ARC EM processors.
+There is a set ARC-specific OpenOCD commands that allow low-level
+access to the core and provide necessary support for ARC extensibility and
+configurability capabilities. ARC processors has much more configuration
+capabilities than most of the other processors and in addition there is an
+extension interface that allows SoC designers to add custom registers and
+instructions. For the OpenOCD that mostly means that set of core and AUX
+registers in target will vary and is not fixed for a particular processor
+model. To enable extensibility several TCL commands are provided that allow to
+describe those optional registers in OpenOCD configuration files. Moreover
+those commands allow for a dynamic target features discovery.
+
+
+@subsection General ARC commands
+
+@deffn {Config Command} {arc add-reg} configparams
+
+Add a new register to processor target. By default newly created register is
+marked as not existing. @var{configparams} must have following required
+arguments:
+
+@itemize @bullet
+
+@item @code{-name} name
+@*Name of a register.
+
+@item @code{-num} number
+@*Architectural register number: core register number or AUX register number.
+
+@item @code{-feature} XML_feature
+@*Name of GDB XML target description feature.
+
+@end itemize
+
+@var{configparams} may have following optional arguments:
+
+@itemize @bullet
+
+@item @code{-gdbnum} number
+@*GDB register number. It is recommended to not assign GDB register number
+manually, because there would be a risk that two register will have same
+number. When register GDB number is not set with this option, then register
+will get a previous register number + 1. This option is required only for those
+registers that must be at particular address expected by GDB.
+
+@item @code{-core}
+@*This option specifies that register is a core registers. If not - this is an
+AUX register. AUX registers and core registers reside in different address
+spaces.
+
+@item @code{-bcr}
+@*This options specifies that register is a BCR register. BCR means Build
+Configuration Registers - this is a special type of AUX registers that are read
+only and non-volatile, that is - they never change their value. Therefore OpenOCD
+never invalidates values of those registers in internal caches. Because BCR is a
+type of AUX registers, this option cannot be used with @code{-core}.
+
+@item @code{-type} type_name
+@*Name of type of this register. This can be either one of the basic GDB types,
+or a custom types described with @command{arc add-reg-type-[flags|struct]}.
+
+@item @code{-g}
+@* If specified then this is a "general" register. General registers are always
+read by OpenOCD on context save (when core has just been halted) and is always
+transferred to GDB client in a response to g-packet. Contrary to this,
+non-general registers are read and sent to GDB client on-demand. In general it
+is not recommended to apply this option to custom registers.
+
+@end itemize
+
+@end deffn
+
+@deffn {Config Command} {arc add-reg-type-flags} -name name flags...
+Adds new register type of ``flags'' class. ``Flags'' types can contain only
+one-bit fields. Each flag definition looks like @code{-flag name bit-position}.
+@end deffn
+
+@anchor{add-reg-type-struct}
+@deffn {Config Command} {arc add-reg-type-struct} -name name structs...
+Adds new register type of ``struct'' class. ``Struct'' types can contain either
+bit-fields or fields of other types, however at the moment only bit fields are
+supported. Structure bit field definition looks like @code{-bitfield name
+startbit endbit}.
+@end deffn
+
+@deffn {Command} {arc get-reg-field} reg-name field-name
+Returns value of bit-field in a register. Register must be ``struct'' register
+type, @xref{add-reg-type-struct}. command definition.
+@end deffn
+
+@deffn {Command} {arc set-reg-exists} reg-names...
+Specify that some register exists. Any amount of names can be passed
+as an argument for a single command invocation.
+@end deffn
+
+@subsection ARC JTAG commands
+
+@deffn {Command} {arc jtag set-aux-reg} regnum value
+This command writes value to AUX register via its number. This command access
+register in target directly via JTAG, bypassing any OpenOCD internal caches,
+therefore it is unsafe to use if that register can be operated by other means.
+
+@end deffn
+
+@deffn {Command} {arc jtag set-core-reg} regnum value
+This command is similar to @command{arc jtag set-aux-reg} but is for core
+registers.
+@end deffn
+
+@deffn {Command} {arc jtag get-aux-reg} regnum
+This command returns the value storded in AUX register via its number. This commands access
+register in target directly via JTAG, bypassing any OpenOCD internal caches,
+therefore it is unsafe to use if that register can be operated by other means.
+
+@end deffn
+
+@deffn {Command} {arc jtag get-core-reg} regnum
+This command is similar to @command{arc jtag get-aux-reg} but is for core
+registers.
+@end deffn
+
+@section STM8 Architecture
+@uref{http://st.com/stm8/, STM8} is a 8-bit microcontroller platform from
+STMicroelectronics, based on a proprietary 8-bit core architecture.
+
+OpenOCD supports debugging STM8 through the STMicroelectronics debug
+protocol SWIM, @pxref{swimtransport,,SWIM}.
+
+@section Xtensa Architecture
+Xtensa processors are based on a modular, highly flexible 32-bit RISC architecture
+that can easily scale from a tiny, cache-less controller or task engine to a high-performance
+SIMD/VLIW DSP provided by Cadence.
+@url{https://www.cadence.com/en_US/home/tools/ip/tensilica-ip/tensilica-xtensa-controllers-and-extensible-processors.html}.
+
+OpenOCD supports generic Xtensa processors implementation which can be customized by
+simply providing vendor-specific core configuration which controls every configurable
+Xtensa architecture option, e.g. number of address registers, exceptions, reduced
+size instructions support, memory banks configuration etc. Also OpenOCD supports SMP
+configurations for Xtensa processors with any number of cores and allows to configure
+their debug signals interconnection (so-called "break/stall networks") which control how
+debug signals are distributed among cores. Xtensa "break networks" are compatible with
+ARM's Cross Trigger Interface (CTI). For debugging code on Xtensa chips OpenOCD
+uses JTAG protocol. Currently OpenOCD implements several Epsressif Xtensa-based chips of
+@uref{https://www.espressif.com/en/products/socs, ESP32 family}.
+
+@subsection General Xtensa Commands
+
+@deffn {Command} {xtensa set_permissive} (0|1)
+By default accessing memory beyond defined regions is forbidden. This commnd controls memory access address check.
+When set to (1), skips access controls and address range check before read/write memory.
+@end deffn
+
+@deffn {Command} {xtensa maskisr} (on|off)
+Selects whether interrupts will be disabled during stepping over single instruction. The default configuration is (off).
+@end deffn
+
+@deffn {Command} {xtensa smpbreak} [none|breakinout|runstall] | [BreakIn] [BreakOut] [RunStallIn] [DebugModeOut]
+Configures debug signals connection ("break network") for currently selected core.
+@itemize @bullet
+@item @code{none} - Core's "break/stall network" is disconnected. Core is not affected by any debug
+signal from other cores.
+@item @code{breakinout} - Core's "break network" is fully connected (break inputs and outputs are enabled).
+Core will receive debug break signals from other cores and send such signals to them. For example when another core
+is stopped due to breakpoint hit this core will be stopped too and vice versa.
+@item @code{runstall} - Core's "stall network" is fully connected (stall inputs and outputs are enabled).
+This feature is not well implemented and tested yet.
+@item @code{BreakIn} - Core's "break-in" signal is enabled.
+Core will receive debug break signals from other cores. For example when another core is
+stopped due to breakpoint hit this core will be stopped too.
+@item @code{BreakOut} - Core's "break-out" signal is enabled.
+Core will send debug break signal to other cores. For example when this core is
+stopped due to breakpoint hit other cores with enabled break-in signals will be stopped too.
+@item @code{RunStallIn} - Core's "runstall-in" signal is enabled.
+This feature is not well implemented and tested yet.
+@item @code{DebugModeOut} - Core's "debugmode-out" signal is enabled.
+This feature is not well implemented and tested yet.
+@end itemize
+@end deffn
+
+@deffn {Command} {xtensa perfmon_enable} <counter_id> <select> [mask] [kernelcnt] [tracelevel]
+Enable and start performance counter.
+@itemize @bullet
+@item @code{counter_id} - Counter ID (0-1).
+@item @code{select} - Selects performance metric to be counted by the counter,
+e.g. 0 - CPU cycles, 2 - retired instructions.
+@item @code{mask} - Selects input subsets to be counted (counter will
+increment only once even if more than one condition corresponding to a mask bit occurs).
+@item @code{kernelcnt} - 0 - count events with "CINTLEVEL <= tracelevel",
+1 - count events with "CINTLEVEL > tracelevel".
+@item @code{tracelevel} - Compares this value to "CINTLEVEL" when deciding
+whether to count.
+@end itemize
+@end deffn
+
+@deffn {Command} {xtensa perfmon_dump} (counter_id)
+Dump performance counter value. If no argument specified, dumps all counters.
+@end deffn
+
+@deffn {Command} {xtensa tracestart} [pc <pcval>/[<maskbitcount>]] [after <n> [ins|words]]
+Set up and start a HW trace. Optionally set PC address range to trigger tracing stop when reached during program execution.
+This command also allows to specify the amount of data to capture after stop trigger activation.
+@itemize @bullet
+@item @code{pcval} - PC value which will trigger trace data collection stop.
+@item @code{maskbitcount} - PC value mask.
+@item @code{n} - Maximum number of instructions/words to capture after trace stop trigger.
+@end itemize
+@end deffn
+
+@deffn {Command} {xtensa tracestop}
+Stop current trace as started by the tracestart command.
+@end deffn
+
+@deffn {Command} {xtensa tracedump} <outfile>
+Dump trace memory to a file.
+@end deffn
+