PCI1221 datasheet(28/123 Pages) TI

28 / 123 page

PCI1221 GHK/PDV

PC CARD CONTROLLERS

SCPS042 – JULY 1998

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

LED socket activity indicators

The socket activity LEDs are provided to indicate when a PC Card is being accessed. The LEDA1 and LEDA2

signals can be routed to the multifunction terminals. When configured for LED outputs, these terminals output

an active high signal to indicate socket activity. LEDA1 indicates socket 0 (card A) activity, and LEDA2 indicates

socket 1 (card B) activity. The LED_SKT output indicates socket activity to either socket 0 or socket 1. Refer

to the

multifunction routing register description on page 62 for details on configuring the multifunction terminals.

The LED signal is active high and is driven for 64-ms durations. When the LED is not being driven high, it is driven

to a low state. Either of the two circuits shown in Figure 7 can be implemented to provide LED signaling, and

it is left for the board designer to implement the circuit that best fits the application.

The LED activity signals are valid when a card is inserted, powered, and not in reset. For PC Card 16, the LED

activity signals are pulsed when READY/IREQ is low. For CardBus cards, the LED activity signals are pulsed

if CFRAME, IRDY, or CREQ are active.

PCI1221

Application-

Specific Delay

Current Limiting

≈ 500 Ω

LED

PCI1221

Current Limiting

≈ 500 Ω

LED

Figure 7. Two Sample LED Circuits

As indicated, the LED signals are driven for a period of 64 ms by a counter circuit. To avoid the possibility of

the LEDs appearing to be stuck when the PCI clock is stopped, the LED signaling is cut-off when the SUSPEND

signal is asserted, when the PCI clock is to be stopped during the clock run protocol, or when in the D2 or D1

power state.

If any additional socket activity occurs during this counter cycle, the counter is reset and the LED signal remains

driven. If socket activity is frequent (at least once every 64 ms), the LED signals remain driven.

CardBus socket registers

The PCI1221 contains all registers for compatibility with the latest PCI-to-PCMCIA CardBus bridge

specification. These registers exist as the CardBus socket registers, and are listed in Table 7.

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