Texas Instruments PCI7611 Integrated Pullup Resistors for PC Card Interface, Spkrout Binaryspkr

3.5.7Integrated Pullup Resistors for PC Card Interface

The PC Card Standard requires pullup resistors on various terminals to support both CardBus and 16-bit PC Card configurations. The PCI7x21/PCI7x11 controller has integrated all of these pullup resistors and requires no additional external components. The I/O buffer on the BVD1(STSCHG)/CSTSCHG terminal has the capability to switch to an internal pullup resistor when a 16-bit PC Card is inserted, or switch to an internal pulldown resistor when a CardBus card is inserted. This prevents inadvertent CSTSCHG events. The pullup resistor requirements for the various UltraMedia interfaces are either included in the UltraMedia cards (or the UltraMedia adapter) or are part of the existing PCMCIA architecture. The PCI7x21/PCI7x11 controller does not require any additional components for UltraMedia support.

3.5.8SPKROUT and CAUDPWM Usage

The SPKROUT terminal carries the digital audio signal from the PC Card to the system. When a 16-bit PC Card is configured for I/O mode, the BVD2 terminal becomes the SPKR input terminal from the card. This terminal, in CardBus applications, is referred to as CAUDIO. SPKR passes a TTL-level binary audio signal to the PCI7x21/PCI7x11 controller. The CardBus CAUDIO signal also can pass a single-amplitude binary waveform as well as a PWM signal. The binary audio signal from each PC Card sockets is enabled by bit 1 (SPKROUTEN) of the card control register (PCI offset 91h, see Section 4.38).

Older controllers support CAUDIO in binary or PWM mode, but use the same output terminal (SPKROUT). Some audio chips may not support both modes on one terminal and may have a separate terminal for binary and PWM. The PCI7x21/PCI7x11 implementation includes a signal for PWM, CAUDPWM, which can be routed to an MFUNC terminal. Bit 2 (AUD2MUX), located in the card control register, is programmed to route a CardBus CAUDIO PWM terminal to CAUDPWM. See Section 4.36, Multifunction Routing Register, for details on configuring the MFUNC terminals.

Figure 3−5 illustrates the SPKROUT connection.

System
Core Logic
	SPKROUT	BINARY_SPKR
		Speaker
PCI7x21/		Subsystem
	CAUDPWM	PWM_SPKR
PCI7x11

Figure 3−5. SPKROUT Connection to Speaker Driver

3.5.9LED 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 A (card A) activity, and LEDA2 indicates socket B (card B) activity. The LED_SKT output indicates socket activity to either socket A or socket B. See Section 4.36, Multifunction Routing Status 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 3−6 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.

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