LPC47N267 datasheet(21/180 Pages) SMSC

21 / 180 page

SMSC DS – LPC47N267

Page 21

Rev. 10/23/2000

7.3.2

Power Management

CLOCKRUN Protocol

See the Low Pin Count (LPC) Interface Specification Reference, Section 8.1.

LPCPD Protocol

The LPC47N267 will function properly if the nLPCPD signal goes active and then inactive again without

nPCI_RESET becoming active. This is a requirement for notebook power management functions.

Although the LPC Bus spec 1.0 section 8.2 states, "After LPCPD# goes back inactive, the LPC I/F will always be

reset using LRST#”, this statement does not apply for mobile systems. LRST# (PCI_RESET#) will not occur if the

LPC Bus power was not removed. For example, when exiting a "light" sleep state (ACPI S1, APM POS), LRST#

(PCI_RESET#) will not occur. When exiting a "deeper" sleep state (ACPI S3-S5, APM STR, STD, soft-off), LRST#

(PCI_RESET#) will occur.

The LPCPD# pin is implemented as a “local” powergood for the LPC bus in the LPC47N267. It is not used as a

global powergood for the chip. It is used to reset the LPC block and hold it in reset.

An internal powergood is implemented in LPC47N267 to minimize power dissipation in the entire chip.

Prior to going to a low-power state, the system will assert the LPCPD# signal. It will go active at least 30

microseconds prior to the LCLK# (PCI_CLK) signal stopping low and power being shut to the other LPC I/F signals.

Upon recognizing LPCPD# active, the LPC47N267 will drive the LDRQ# signal low or tri-state, and do so until

LPCPD# goes back active.

Upon recognizing LPCPD# inactive, the LPC47N267 will drive its LDRQ# signal high.

See the Low Pin Count (LPC) Interface Specification Reference, Section 8.2.

SYNC Protocol

See the Low Pin Count (LPC) Interface Specification Reference, Section 4.2.1.8 for a table of valid SYNC values.

Typical Usage

The SYNC pattern is used to add wait states. For read cycles, the LPC47N267 immediately drives the SYNC pattern

upon recognizing the cycle. The host immediately drives the sync pattern for write cycles. If the LPC47N267 needs

to assert wait states, it does so by driving 0101 or 0110 on LAD[3:0] until it is ready, at which point it will drive 0000 or

1001. The LPC47N267 will choose to assert 0101 or 0110, but not switch between the two patterns.

The data (or wait state SYNC) will immediately follow the 0000 or 1001 value.

The SYNC value of 0101 is intended to be used for normal wait states, wherein the cycle will complete within a few

clocks. The LPC47N267 uses a SYNC of 0101 for all wait states in a DMA transfer.

The SYNC value of 0110 is intended to be used where the number of wait states is large. This is provided for EPP

cycles, where the number of wait states could be quite large (>1 microsecond). However, the LPC47N267 uses a

SYNC of 0110 for all wait states in an I/O transfer.

The SYNC value is driven within 3 clocks.

SYNC Timeout

The SYNC value is driven within 3 clocks. If the host observes 3 consecutive clocks without a valid SYNC pattern, it

will abort the cycle.

The LPC47N267 does not assume any particular timeout. When the host is driving SYNC, it may have to insert a

very large number of wait states, depending on PCI latencies and retries.

SYNC Patterns and Maximum Number of SYNCS

If the SYNC pattern is 0101, then the host assumes that the maximum number of SYNCs is 8.

If the SYNC pattern is 0110, then no maximum number of SYNCs is assumed. The LPC47N267 has protection

mechanisms to complete the cycle. This is used for EPP data transfers and will utilize the same timeout protection

that is in EPP.

LPC47N267 Datasheet(PDF) 21 Page - SMSC Corporation

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