In-System Debugging—IP2022 User’s Manual 328 www.ubicom.com 5.1 Debugging Modes When using a debugger, the IP2022 has two modes: • Run mode—free-running program execution • Break mode—CPU stopped In  Break  mode,  the  instruction  pipeline  is  flushed  and  NOP
instructions are executed continuously without incrementing the
PC, which has the effect of stalling program execution. There are
three conditions which cause the IP2022 to enter Break mode: • Issuing  an  INITIALIZE  or  BREAK  command  through  the
ISD/ISP interface. • Triggering a hardware breakpoint set up using the SET_BKPT
command. • Executing a break instruction (an IP2022 instruction, not to
be confused with the BREAK command on the ISD/ISP inter-
face). If Break mode is entered by triggering the hardware breakpoint or
executing the break instruction, the CPU is stalled with the PC
pointing  to the instruction that triggered entry into Break mode.
When triggered by a hardware breakpoint, the instruction at the
breakpoint address is not executed before entering Break mode.
Unlike interrupts, no registers are saved or restored on entry or
exit from Break mode.