PCI1520GHK Datasheet, PDF (45/139 Pages) Texas Instruments – PC Card Controllers

System
Core Logic
SPKROUT
PCI1520
CAUDPWM
BINARY_SPKR
Speaker
Subsystem
PWM_SPKR
Figure 3−6. Sample Application of SPKROUT and CAUDPWM
3.5.8 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. See Section 4.30, Multifunction
Routing Register, for details on configuring the multifunction terminals.
The active-high LED signal is driven for 64-ms. When the LED is not being driven high, it is driven to a low state. Either
of the two circuits shown in Figure 3−7 can be implemented to provide LED signaling, and the board designer must
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.
Current Limiting
R ≈ 500 Ω
PCI1520
LED
PCI1520
Application-
Specific Delay
Current Limiting
R ≈ 500 Ω
LED
Figure 3−7. 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, then the counter is reset and the LED signal remains
driven. If socket activity is frequent (at least once every 64 ms), then the LED signals remain driven.
3.5.9 CardBus Socket Registers
The PCI1520 contains all registers for compatibility with the 1997 PC Card Standard. These registers exist as the
CardBus socket registers and are listed in Table 3−6.
3−10