Peripheral devices communicate with the CPU by means of IRQs, or Interrupt ReQuest. Interrupts are signals that a previous request has been serviced, data has arrived that needs to be interpreted, or an error has been detected. When the CPU receives an interrupt, it halts what it is doing to handle the necessary task. Interrupts are sent over one of the 15 IRQ wires on the computer's bus. If two peripherals are set to use the same IRQ, and do so at the same time, a short is produced in the bus. While this most likely will have no effect, it has a chance of damaging the device or motherboard. Some I/O and controller cards as well as many devices have alternate IRQs, resulting in a solution to IRQ conflicts. The COM port that a modem is connected to also has an IRQ assigned to it. If modems are assigned to the same IRQs as other devices, they must use an alternate IRQ. Fortunately, many of today's modems are capable of addressing alternate IRQs. It is very important when assigning IRQs to make sure no two devices will need the same IRQ at the same time.
Articles in this section
- How can I use one phone line for both voice and data?
- How do V.92 modem speeds compare to ISDN, ADSL and Cable speeds?
- Does the Model 3090A modem have lights or a speaker ?
- Where can I learn more about modems and V.92/V.44?
- What makes a Zoom V.92 modem faster than V.90?
- Synchronous vs. Asynchronous Data Transfer
- IRQ Settings
- COM Port Settings (DOS/Windows)
- UARTs and Data Buffering
- Flow Control