LPC47M192 datasheet(28/228 Pages) SMSC

28 / 228 page

SMSC DS – LPC47M192

Page 28

Rev. 03/30/05

DATASHEET

7.3 LPC Interface

The following sub-sections specify the implementation of the LPC bus.

7.3.1 LPC INTERFACE SIGNAL DEFINITION

The signals required for the LPC bus interface are described in the table below. LPC bus signals use PCI

33MHz electrical signal characteristics.

SIGNAL

NAME

TYPE

DESCRIPTION

LAD[3:0]

I/O

LPC address/data bus. Multiplexed command, address and data bus.

LFRAME#

Input

Frame signal. Indicates start of new cycle and termination of broken cycle

PCI_RESET#

Input

PCI Reset. Used as LPC Interface Reset.

LDRQ#

Output

Encoded DMA/Bus Master request for the LPC interface.

nIO_PME

Power Mgt Event signal. Allows the LPC47M192 to request wakeup.

LPCPD#

Input

Powerdown Signal. Indicates that the LPC47M192 should prepare for power to be shut

on the LPC interface.

SER_IRQ

I/O

Serial IRQ.

PCI_CLK

Input

PCI Clock.

Note: The CLKRUN# signal is not implemented in this part.

7.3.2 LPC CYCLES

The following cycle types are supported by the LPC protocol.

CYCLE TYPE

TRANSFER SIZE

I/O Write

1 Byte

I/O Read

1 Byte

DMA Write

1 Byte

DMA Read

1 Byte

LPC47M192 ignores cycles that it does not support.

7.3.3 FIELD DEFINITIONS

The data transfers are based on specific fields that are used in various combinations, depending on the cycle

type. These fields are driven onto the LAD[3:0] signal lines to communicate address, control and data

information over the LPC bus between the host and the LPC47M192. See the Low Pin Count (LPC) Interface

Specification Revision 1.0 from Intel, Section 4.2 for definition of these fields.

7.3.4 LFRAME# USAGE

LFRAME# is used by the host to indicate the start of cycles and the termination of cycles due to an abort or

time-out condition. This signal is to be used by the LPC47M192 to know when to monitor the bus for a cycle.

This signal is used as a general notification that the LAD[3:0] lines contain information relative to the start or

stop of a cycle, and that the LPC47M192 monitors the bus to determine whether the cycle is intended for it.

The use of LFRAME# allows the LPC47M192 to enter a lower power state internally. There is no need for the

LPC47M192 to monitor the bus when it is inactive, so it can decouple its state machines from the bus, and

internally gate its clocks.

When the LPC47M192 samples LFRAME# active, it immediately stops driving the LAD[3:0] signal lines on the

next clock and monitor the bus for new cycle information.

The LFRAME# signal functions as described in the Low Pin Count (LPC) Interface Specification, Revision 1.0.

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