The RVI unit comprises a v2 Low Voltage Differential Signaling (LVDS) probe. The probe is visibly different by the presence of two colored LEDs that signify the status of the activity taking place.

The functionality of the v3.1 probe enables you to make a Serial Wire Debug (SWD) connection to the Debug Access Port (DAP).

The following figure shows the dimensions of the LVDS probe and its LED locations:

The following table provides a diagnostic means to determine the type of activity taking place, according to the permutations of the green and yellow LEDs:

RVI v4.0 supports the SWD debugging protocol as an alternative to JTAG. SWD can only be used with the LVDS probe, and without using the JTAG ribbon cable. The probe must be a v2 type as described, and you might have to upgrade its firmware.

As shown in the previous figure, compatible probes have two LEDs on their front left-hand side. At power-up, both LEDs are lit. If only the yellow LED is lit, you must upgrade the probe to make it SWD-capable.

In addition, if your probe does not appear to have a CPLD located as shown in the previous figure, it means that your probe is of the v1.5 type, and must be replaced if SWD-compatibility is required. To upgrade your probe to the v2 type, contact ARM for more information.

SWD supports only a single DAP and not a chain of devices. The graphical representation of the target system changes to represent this when SWD is selected.