ULINKPRO Keil, ULINKPRO Datasheet - Page 51

• Manufacturer Part Number: ULINKPRO
• Description: KIT DEBUG/TRACE UNIT HIGH SPEED
• Manufacturer: Keil
• Type: In-Circuit, Real-Time Debugger/Programmerr

Specifications of ULINKPRO

• Contents: Module
• For Use With/related Products: ARM7, ARM9, Cortex
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

50
RTX ensures that interrupts execute correctly and leaves the machine in a well-
defined state. Interrupt service routines, also known as interrupt handlers, are
used to service hardware devices and transitions between operation modes, such
as system calls, system timers, disk I/O, power signals, keystrokes, watchdogs;
other interrupts transfer data using UART or Ethernet.
Hints for working with interrupt functions in RTX:
Another important concept is the interrupt latency, which is defined as the period
between the generation and servicing of that interrupt. This is especially
important in systems that need to control machinery in real time, and therefore
require low interrupt latency. RTX ensures that a subroutine will finish its
execution in an agreed maximum length of time and that the interrupt latency
does not exceed a predefined maximum length of time.
The general logic of an ISR looks like the following code example. The interrupt
function ext0_int sends an event to process_task and exits. The task
process_task processes the external interrupt event. In this example,
process_task is simple and only counts the number of interrupt events.
Functions that begin with os_ can be called from a task but not from an
interrupt service routine
Functions that begin with isr_ can be called from an IRQ interrupt service
routine but not from a task. Never use them from FIQ.
Never enable any IRQ interrupt that calls isr_ functions before the kernel has
been started
Avoid nesting IRQ functions on ARM7/ARM9 targets
Use short IRQ functions to send signals and messages to RTOS tasks
Interrupt functions are added to applications the same way as in non-RTX
projects
By default, interrupts are globally enabled at startup
Chapter 4. RTX RTOS Kernel