RTX51 Tiny User's Guide

Long Interrupts

Typically, Interrupt Service Routines (ISRs) are designed to execute quickly. In some situations your ISRs may excute for a long period of time. If a high-priority ISR executes longer than the RTX51 timer tick interval, the RTX51 timer interrupt may be interrupted (by your ISR) and may be reentered (by a subsequent RTX51 timer interrupt).

If you use high priority interrupts that execute for long periods of time, you should consider reducing the amount of work performed in your ISR, changing the RTX51 Timer Tick rate to one that is slower, or using the following configuration option.

• LONG_USR_INTR specifies whether or not the application has interrupts (other than the RTX51 Tiny Timer Tick Interrupt) that execute longer than a timer tick interval. When this configuration option is set to a value of 1, RTX51 Tiny includes code to protect the RTX51 Tiny Timer Tick Interrupt from reentrancy. The default setting is 0 for fast interrupts.