+@section Low Level JTAG Commands
+
+These commands are used by developers who need to access
+JTAG instruction or data registers, possibly controlling
+the order of TAP state transitions.
+If you're not debugging OpenOCD internals, or bringing up a
+new JTAG adapter or a new type of TAP device (like a CPU or
+JTAG router), you probably won't need to use these commands.
+
+@deffn Command {drscan} tap [numbits value]+ [@option{-endstate} tap_state]
+Loads the data register of @var{tap} with a series of bit fields
+that specify the entire register.
+Each field is @var{numbits} bits long with
+a numeric @var{value} (hexadecimal encouraged).
+The return value holds the original value of each
+of those fields.
+
+For example, a 38 bit number might be specified as one
+field of 32 bits then one of 6 bits.
+@emph{For portability, never pass fields which are more
+than 32 bits long. Many OpenOCD implementations do not
+support 64-bit (or larger) integer values.}
+
+All TAPs other than @var{tap} must be in BYPASS mode.
+The single bit in their data registers does not matter.
+
+When @var{tap_state} is specified, the JTAG state machine is left
+in that state.
+For example @sc{drpause} might be specified, so that more
+instructions can be issued before re-entering the @sc{run/idle} state.
+If the end state is not specified, the @sc{run/idle} state is entered.
+
+@quotation Warning
+OpenOCD does not record information about data register lengths,
+so @emph{it is important that you get the bit field lengths right}.
+Remember that different JTAG instructions refer to different
+data registers, which may have different lengths.
+Moreover, those lengths may not be fixed;
+the SCAN_N instruction can change the length of
+the register accessed by the INTEST instruction
+(by connecting a different scan chain).
+@end quotation
+@end deffn
+
+@deffn Command {flush_count}
+Returns the number of times the JTAG queue has been flushed.
+This may be used for performance tuning.
+
+For example, flushing a queue over USB involves a
+minimum latency, often several milliseconds, which does
+not change with the amount of data which is written.
+You may be able to identify performance problems by finding
+tasks which waste bandwidth by flushing small transfers too often,
+instead of batching them into larger operations.
+@end deffn
+
+@deffn Command {irscan} [tap instruction]+ [@option{-endstate} tap_state]
+For each @var{tap} listed, loads the instruction register
+with its associated numeric @var{instruction}.
+(The number of bits in that instruction may be displayed
+using the @command{scan_chain} command.)
+For other TAPs, a BYPASS instruction is loaded.
+
+When @var{tap_state} is specified, the JTAG state machine is left
+in that state.
+For example @sc{irpause} might be specified, so the data register
+can be loaded before re-entering the @sc{run/idle} state.
+If the end state is not specified, the @sc{run/idle} state is entered.
+
+@quotation Note
+OpenOCD currently supports only a single field for instruction
+register values, unlike data register values.
+For TAPs where the instruction register length is more than 32 bits,
+portable scripts currently must issue only BYPASS instructions.
+@end quotation
+@end deffn
+
+@deffn Command {jtag_reset} trst srst
+Set values of reset signals.
+The @var{trst} and @var{srst} parameter values may be
+@option{0}, indicating that reset is inactive (pulled or driven high),
+or @option{1}, indicating it is active (pulled or driven low).
+The @command{reset_config} command should already have been used
+to configure how the board and JTAG adapter treat these two
+signals, and to say if either signal is even present.
+@xref{Reset Configuration}.
+@end deffn
+
+@deffn Command {runtest} @var{num_cycles}
+Move to the @sc{run/idle} state, and execute at least
+@var{num_cycles} of the JTAG clock (TCK).
+Instructions often need some time
+to execute before they take effect.
+@end deffn
+
+@c tms_sequence (short|long)
+@c ... temporary, debug-only, probably gone before 0.2 ships
+
+@deffn Command {verify_ircapture} (@option{enable}|@option{disable})
+Verify values captured during @sc{ircapture} and returned
+during IR scans. Default is enabled, but this can be
+overridden by @command{verify_jtag}.
+@end deffn
+
+@deffn Command {verify_jtag} (@option{enable}|@option{disable})
+Enables verification of DR and IR scans, to help detect
+programming errors. For IR scans, @command{verify_ircapture}
+must also be enabled.
+Default is enabled.
+@end deffn
+
+@section TAP state names
+@cindex TAP state names
+
+The @var{tap_state} names used by OpenOCD in the @command{drscan},
+and @command{irscan} commands are:
+