PCI1520 datasheet(44/138 Pages) TI

44 / 138 page

3−8

There are two types of PC Card controllers to consider.

•

Legacy controller not using the standardized ZV register model

Software reads bit 10 (STDZVREG) of the socket control register (CardBus socket address + 10h) to

determine if the standardized zoomed-video register model is supported. If the bit returns 0, then software

must use legacy code to enable zoomed video.

•

Newer controller that uses the standardized ZV register model

Software reads bit 10 (STDZVREG) of the socket control register (CardBus socket address + 10h) to

determine if the standardized zoomed-video register model is supported. If the bit returns 1, then software

can use the process/register model detailed in Table 3−4 to enable zoomed video.

Table 3−4. Zoomed-Video Card Interrogation

ZVSUPPORT

(this socket)

ZVSUPPORT

(other socket)

ZV_ACTIVITY

ACTION

Set ZVEN to enable zoomed video.

Display a user message such as, “The zoomed video protocol required by this PC

Card application is already in use by another card.”

Display a user message such as, “This platform does not support the zoomed-video

protocol required by this PC Card application.”

Display a user message such as, “This platform does not support the zoomed-video

protocol required by this PC Card application in this PC Card socket. Please remove

the card and re-insert in the other PC Card socket.”

3.5.5

Internal Ring Oscillator

The internal ring oscillator provides an internal clock source for the PCI1520 so that neither the PCI clock nor an

external clock is required in order for the PCI1520 to power down a socket or interrogate a PC Card. This internal

oscillator, operating nominally at 16 kHz, can be enabled by setting bit 27 (P2CCLK) of the system control register

(PCI offset 80h, see Section 4.29) to 1. This function is disabled by default.

3.5.6

Integrated Pullup Resistors

The PC Card Standard (release 7.1) requires pullup resistors on various terminals to support both CardBus and 16-bit

card configurations. Unlike the PCI12XX, PCI1450, and PCI4450 which required external pullup resistors, the

PCI1520 has integrated all of these pullup resistors. The I/O buffer on the BVD1(STSCHG)/CSTSCHG terminal has

the capability to switch either pullup or pulldown. The pullup resistor is turned on when a 16-bit PC Card is inserted,

and the pulldown resistor is turned on when a CardBus PC Card is inserted. This prevents unexpected CSTSCHG

signal assertion. The integrated pullup resistors are listed in Table 3−5.

PCI1520 Datasheet(PDF) 44 Page - Texas Instruments