+@deffn Command {transport select} transport_name
+Select which of the supported transports to use in this OpenOCD session.
+The transport must be supported by the debug adapter hardware and by the
+version of OPenOCD you are using (including the adapter's driver).
+No arguments: returns name of session's selected transport.
+@end deffn
+
+@subsection JTAG Transport
+@cindex JTAG
+JTAG is the original transport supported by OpenOCD, and most
+of the OpenOCD commands support it.
+JTAG transports expose a chain of one or more Test Access Points (TAPs),
+each of which must be explicitly declared.
+JTAG supports both debugging and boundary scan testing.
+Flash programming support is built on top of debug support.
+@subsection SWD Transport
+@cindex SWD
+@cindex Serial Wire Debug
+SWD (Serial Wire Debug) is an ARM-specific transport which exposes one
+Debug Access Point (DAP, which must be explicitly declared.
+(SWD uses fewer signal wires than JTAG.)
+SWD is debug-oriented, and does not support boundary scan testing.
+Flash programming support is built on top of debug support.
+(Some processors support both JTAG and SWD.)
+@deffn Command {swd newdap} ...
+Declares a single DAP which uses SWD transport.
+Parameters are currently the same as "jtag newtap" but this is
+expected to change.
+@end deffn
+@deffn Command {swd wcr trn prescale}
+Updates TRN (turnaraound delay) and prescaling.fields of the
+Wire Control Register (WCR).
+No parameters: displays current settings.
+@end deffn
+
+@subsection SPI Transport
+@cindex SPI
+@cindex Serial Peripheral Interface
+The Serial Peripheral Interface (SPI) is a general purpose transport
+which uses four wire signaling. Some processors use it as part of a
+solution for flash programming.
+