PCI1420 datasheet(51/137 Pages) TI

51 / 137 page

3–21

It should also be noted that asynchronous signals, such as card status change interrupts and RI_OUT, can be passed

to the host system without a PCI clock. However, if card status change interrupts are routed over the serial interrupt

stream, then the PCI clock will have to be restarted in order to pass the interrupt, because neither the internal oscillator

nor an external clock is routed to the serial interrupt state machine. Figure 3–18 is a functional implementation

diagram.

PCI1420

Core

RESET

SUSPEND

GNT

PCLK

PCLKIN

RESETIN

SUSPENDIN

Figure 3–18. Suspend Functional Implementation

Figure 3–19 is a signal diagram of the suspend function.

RESET

GNT

SUSPEND

PCLK

RESETIN

SUSPENDIN

PCLKIN

External Terminals

Internal Signals

Figure 3–19. Signal Diagram of Suspend Function

3.8.5

Requirements for Suspend Mode

The suspend mode prevents the clearing of all register contents on the assertion of reset (PRST or GRST) which

would require the reconfiguration of the PCI1420 by software. Asserting the SUSPEND signal places the controller’s

PCI outputs in a high impedance state and gates the PCLK signal internally to the controller unless a PCI transaction

is currently in process (GNT is asserted). It is important that the PCI bus not be parked on the PCI1420 when

SUSPEND is asserted because the outputs are in a high impedance state.

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

appropriate PCI1420 registers.

PCI1420 Datasheet(PDF) 51 Page - Texas Instruments