3.7 Programmable Interrupt Subsystem
Interrupts provide a way for I/O devices to let the microprocessor know that they require servicing. The dynamic
nature of PC Cards and the abundance of PC Card I/O applications require substantial interrupt support from the
PCI6x21/PCI6x11 controller. The PCI6x21/PCI6x11 controller provides several interrupt signaling schemes to
accommodate the needs of a variety of platforms. The different mechanisms for dealing with interrupts in this
controller are based on various specifications and industry standards. The ExCA register set provides interrupt
control for some 16-bit PC Card functions, and the CardBus socket register set provides interrupt control for the
CardBus PC Card functions. The PCI6x21/PCI6x11 controller is, therefore, backward compatible with existing
interrupt control register definitions, and new registers have been defined where required.
The PCI6x21/PCI6x11 controller detects PC Card interrupts and events at the PC Card interface and notifies the host
controller using one of several interrupt signaling protocols. To simplify the discussion of interrupts in the
PCI6x21/PCI6x11 controller, PC Card interrupts are classified either as card status change (CSC) or as functional
interrupts.
The method by which any type of PCI6x21/PCI6x11 interrupt is communicated to the host interrupt controller varies
from system to system. The PCI6x21/PCI6x11 controller offers system designers the choice of using parallel PCI
interrupt signaling, parallel ISA-type IRQ interrupt signaling, or the IRQSER serialized ISA and/or PCI interrupt
protocol. It is possible to use the parallel PCI interrupts in combination with either parallel IRQs or serialized IRQs,
as detailed in the sections that follow. All interrupt signaling is provided through the seven multifunction terminals,
MFUNC0−MFUNC6.
3.7.1 PC Card Functional and Card Status Change Interrupts
PC Card functional interrupts are defined as requests from a PC Card application for interrupt service and are
indicated by asserting specially-defined signals on the PC Card interface. Functional interrupts are generated by
16-bit I/O PC Cards and by CardBus PC Cards.
Card status change (CSC)-type interrupts are defined as events at the PC Card interface that are detected by the
PCI6x21/PCI6x11 controller and may warrant notification of host card and socket services software for service. CSC
events include both card insertion and removal from PC Card sockets, as well as transitions of certain PC Card
signals.
Table 3−9 summarizes the sources of PC Card interrupts and the type of card associated with them. CSC and
functional interrupt sources are dependent on the type of card inserted in the PC Card socket. The four types of cards
that can be inserted into any PC Card socket are:
•
•
•
•
16-bit memory card
16-bit I/O card
CardBus cards
UltraMedia card
3−15
TI [ TEXAS INSTRUMENTS ]
