Antonio Borneo fc8f939d95 Support two-wire cJTAG OSCAN1 and JScan3 using FTDI adapters ...

cJTAG OSCAN1, in lieu of 4-wire JTAG, is starting to be a configuration
option for some SiFive hardware. An FTDI-based adapter that can be
configured to drive the bidirectional pin TMSC is assumed for this
topology. Specifically, the Olimex ARM-USB-TINY-H with the ARM-JTAG-SWD
adapter, connected to a SiFive cJTAG-enabled target board is the only
known concrete topology, currently. But in theory, other FTDI based
devices that can drive a two-wire bidirectional signaling pattern could
be made to work in this scheme in the future.

These code changes are offered as a way to drive that topology. It's
translating IR/DR and JTAG traversal commands to the two-wire clocking
and signaling.

See:
- https://github.com/riscv-collab/riscv-openocd/pull/320
- https://github.com/riscv-collab/riscv-openocd/pull/736

Signed-off-by: Greg Savin <greg.savin@sifive.com>
Signed-off-by: mrv96 <mrv96@users.noreply.github.com>
Signed-off-by: Tim Newsome <tim@sifive.com>
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Change-Id: Ia1daa2c01227c4b0005be947b2bb0de81a800874
Reviewed-on: https://review.openocd.org/c/openocd/+/6981
Tested-by: jenkins

2025-11-30 10:23:52 +00:00

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