Signal Definition
R
10 251289-001
Signal Peripheral Host Description
LPCPD# I O Power Down: Indicates that the peripheral should
prepare for power to be removed from the LPC I/F
devices. Actual power removal is system dependent. This
signal is optional for the host.
LSMI# OD I SMI#: Only needed if peripheral want to cause SMI# on
an I/O instruction for retry. Otherwise can use SMI# via
SERIRQ. This signal is optional for the host.
In comparison with existing ISA-based devices, the signal savings is substantial. The LPC
interface will generally only require 6 new signals: LAD[0:3], LFRAME#, and LDRQ#.
CLKRUN# is typically only implemented in mobile systems. LPCPD# is only needed for LPC
devices that are partially powered during certain low-power states.
At a minimum, the following ISA/X-bus signals found on plug-n-play devices are no longer
needed:
D[7:0], SA[15:0], DREQ[3:0], DACK#[3:0], TC, IOR#, IOW#, IOCHRDY 36 signals
Net Savings on Peripheral: 30
On 16 bit ISA based devices, the IOCS16# and MEMCS# signals are also saved. If the serial IRQ
was not previously supported, and if 16 bit DMA channels are used by the peripheral, several more
pins are saved. The net effect is that a fully functional Super I/O device that may have required a
160 pin package to implement can now fit in an 88 pin or less size package by using the LPC
interface.