The EVTI and EVTO pins are not accessible on the Atmel JTAGICE3.
However, they can still be used in conjunction with other external equipment.
EVTI can be used for the following purposes:
- The target can be forced to
stop execution in response to an external event. If the Event In Control (EIC) bits in
the DC register are written to 0b01, high-to-low transition on the EVTI pin will
generate a breakpoint condition. EVTI must remain low for one CPU clock cycle to
guarantee that a breakpoint is triggered. The External Breakpoint bit (EXB) in DS is set
when this occurs.
- Generating trace
synchronization messages. Not used by the JTAGICE3.
EVTO can be used for the following purposes:
- Indicating that the CPU has
entered debug mode. Setting the EOS bits in DC to 0b01 causes the EVTO pin to be pulled
low for one CPU clock cycle when the target device enters debug mode. This signal can be
used as a trigger source for an external oscilloscope.
- Indicating that the CPU has
reached a breakpoint or watchpoint. By setting the EOC bit in a corresponding
Breakpoint/Watchpoint Control Register, breakpoint or watchpoint status is indicated on
the EVTO pin. The EOS bits in DC must be set to 0xb10 to enable this feature. The EVTO
pin can then be connected to an external oscilloscope in order to examine watchpoint
timing.
- Generating trace timing
signals. Not used by the JTAGICE3.