PCI4451 datasheet(67/216 Pages) TI

67 / 216 page

3–23

3.6.7

Requirements for SUSPEND

A requirement for implementing suspend mode is that the PCI bus must not be parked on the PCI4451 when

SUSPEND is asserted. The PCI4451 responds to SUSPEND being asserted by placing the REQ terminal in a

high-impedance state. The PCI4451 will also gate the internal clock and reset.

The GPIOs, MFUNC signals, and RI_OUT signals are all active during SUSPEND, unless they are disabled in the

appropriate PCI4451 registers.

3.6.8

Ring Indicate

The RI_OUT output is an important feature used in legacy power management. It is used so that a system can go

into a suspended mode and wake up on modem rings and other card events. The RI_OUT signal on the PCI4451

may be asserted under any of the following conditions:

•

A 16-bit PC Card modem in a powered socket asserts RI to indicate an incoming call to the system.

•

A powered down CardBus card asserts CSTSCHG (CBWAKE) requesting system and interface wake up.

•

A card status change (CSC) event, such as insertion/removal of cards, battery voltage levels, occurs.

A CSTSCHG signal from a powered CardBus card is indicated as a CSC event, not as a CBWAKE event. These two

RI_OUT events are enabled separately. The following figure details various enable bits for the PCI4451 RI_OUT

function; however, it does not illustrate the masking of CSC events. See Interrupt Masks and Flags, Section 3.5.2,

for a detailed description of CSC interrupt masks and flags.

RI_OUT is multiplexed on the same terminal with PME. The default is for RI_OUT to be signaled on this terminal.

In PCI power managed systems, the PME signal should be enabled by setting bit 0 (RI_OUT/PME) in the system

control register (PCI offset 80h, see Section 4.28) and clearing bit 7 (RIENB) in the card control register (PCI offset

91h, see Section 4.38).

RIENB

RICSC(A)

RI_OUT

PC Card

Socket 0

PC Card

Socket 1

Card

I/F

16-bit

Card

Bus

Card

I/F

16-bIt

Card

Bus

RICSC(B)

RI_OUT Function

CBWAKE

CSC

CBWAKE

CSC

Figure 3–17. RI_OUT Functional Illustration

Routing of CSC events to the RI_OUT signal, enabled on a per-socket basis, is programmed by the RICSC bit in the

card control register (PCI offset 91h, see Section 4.38). This bit is socket-dependent (not shared), as illustrated in

Figure 3–17.

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