ISA-to-PC-Card (PCMCIA) Controllers — PD6710/’22
Connection of Interrupt Pins
IRQ interrupts in PC-compatible systems are not generally shared by hardware. Therefore, each
device in the system using IRQ interrupts must have a unique interrupt line. Additionally, many
software applications assume that certain I/O devices use specific IRQ signals. To allow PC Cards
with differing I/O functionalities to be connected to appropriate nonconflicting IRQ locations, the
PD67XX can steer the interrupt signal from a PC Card to any one of the ten different hardware
interrupt lines.
For some I/O-type cards, software is written so that IRQ interrupts can be shared. The PD67XX
contains unique logic that allows IRQ interrupts to be shared under software control. This is
accomplished by programming the PD67XX to alternately pulse and then three-state the desired
interrupt pin, which has been programmed as an IRQ output. This unique IRQ interrupt sharing
technique can be controlled through software so that systems incapable of IRQ sharing have no
loss of functionality.
4.1.5
Alternate Functions of Interrupt Pins
The PD67XX has two interrupt pins that can be programmed for alternate functions: IRQ12/
LED_OUT* and IRQ15/RI_OUT*. In addition, the PD6722 allows IRQ9 and IRQ10 to be
programmed for system DMA transfer handshake functions.
4.1.5.1
IRQ12 as LED_OUT* Driver
If a disk-activity or card-cycle-activity indicator is desired, IRQ12/LED_OUT* can be
programmed as an open-collector LED driver, capable of driving most common LEDs. There is no
specific bit that programs the IRQ12 pin to become an LED driver; instead, whenever a socket
interface is programmed to support a drive status LED input or is programmed to show card
activity on the LED (as described below), the IRQ12 pin becomes reconfigured as an open-
collector LED driver.
The Extension Control 1 register’s LED Activity Enable bit (extended index 03h bit 2) is used to
enable the LED being used to show card activity. When this bit is set, any type of read or write
cycles to the respective socket cause the IRQ12/LED_OUT* signal to be driven low for the
duration of the card activity.
The Drive LED Enable bit (Misc Control 2 register bit 4) is used to enable the BVD2/-SPKR/-
LED input from an I/O-interfaced card to be interpreted as a drive LED input, where an open-
collector signal driven low on this input will cause the IRQ12/LED_OUT* open-collector output to
go low.
Any combination of settings of LED Activity Enable and Drive LED Enable bits can be used on
each socket, with each type of activity being able to separately cause the LED to be illuminated.
Status from non-present or non-activated cards is automatically masked off from causing the
IRQ12/LED_OUT* signal to be driven low.
4.1.5.2
IRQ15 as RI_OUT*
If the capability to ‘wake up’ a system on an incoming phone call to a PC Card modem is desired,
it may be necessary in some systems to use a dedicated wakeup signal to the system’s SMI or NMI
controller to facilitate this instead of using the normal interrupt connections. If this is the case, the
IRQ15 connection can be reprogrammed to pass through a qualified version of an I/O interfaced
card’s -RI signal.
Datasheet
31
INTEL [ INTEL ]
