Operaon
User Guide
© 2023 Microchip Technology Inc. and its subsidiaries
DS-50003529B - 37
support breakpoints during debugging, the debugger must insert a BREAK instruction into FLASH
at the point at which the users request a breakpoint. The original instruction must be cached for
later replacement. When single-stepping over a BREAK instruction, the debugger has to execute
the original cached instruction to preserve program behavior. In extreme cases, the BREAK has to
be removed from FLASH and replaced later. All these scenarios can cause apparent delays when
single-stepping from breakpoints, which will be exacerbated when the target clock frequency is very
low.
It is thus recommended to observe the following guidelines, where possible:
• Always run the target at as high a frequency as possible during debugging. The debugWIRE
physical interface is clocked from the target clock.
• Try to minimize the number of breakpoint additions and removals, as each one requires a FLASH
page to be replaced on the target.
• Try to add or remove a small number of breakpoints at a time, to minimize the number of FLASH
page write operations.
• If possible, avoid placing breakpoints on double-word instructions.
4.3.1.5.3 Understanding debugWIRE and the DWEN Fuse
When enabled, the debugWIRE interface takes control of the device’s RESET pin, which makes it
mutually exclusive to the SPI interface, which also needs this pin. When enabling and disabling the
debugWIRE module, follow one of these two approaches:
• Let the software front-end take care of things (recommended)
• Set and clear DWEN manually (exercise caution, advanced users only!)
Important: When manipulating DWEN manually, the SPIEN fuse must remain set to avoid
having to use High-Voltage programming.
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