ISP1505CBS datasheet(15/76 Pages) NXP

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ISP1505A_ISP1505C_3

Product data sheet

Rev. 03 — 26 August 2008

14 of 75

NXP Semiconductors

ISP1505A; ISP1505C

ULPI HS USB host and peripheral transceiver

8.1.2 Low-power mode

When the USB is idle, the link can place the ISP1505 into low-power mode (also called

suspend mode). In low-power mode, the data bus deﬁnition changes to that shown in

Table 4. To enter low-power mode, the link sets the SUSPENDM bit in the Function

Control register to logic 0. To exit low-power mode, the link asserts the STP signal. The

ISP1505 will draw only suspend current from the VCC supply (see Table 44).

During low-power mode, the clock on XTAL1 may be stopped. The clock must be started

again before asserting STP to exit low-power mode. After exiting low-power mode, the

ISP1505 will send an RXCMD to the link if a change was detected in any interrupt source,

and the change still exists. An RXCMD may not be sent if the interrupt condition is

removed before exiting.

For more information on low-power mode enter and exit protocols, refer to

UTMI+ Low Pin

Interface (ULPI) Speciﬁcation Rev. 1.1.

DIR

Direction: Controls the direction of data bus DATA[7:0]. In synchronous

mode, the ISP1505 drives DIR to LOW by default, making the data bus

an input so that the ISP1505 can listen for TXCMDs from the link. The

ISP1505 drives DIR to HIGH only when it has data for the link. When

DIR and NXT are HIGH, the byte on the data bus contains decoded

USB data. When DIR is HIGH and NXT is LOW, the byte contains

status information called RXCMD (receive command). The only

exception to this rule is when the PHY returns register read data, where

NXT is also LOW, replacing the usual RXCMD byte. Every change in

DIR causes a turnaround cycle on the data bus, during which DATA[7:0]

is not valid and must be ignored by the link.

DIR is always asserted during low-power and serial modes.

STP

Stop: In synchronous mode, the link drives STP to HIGH for one cycle

after the last byte of data is sent to the ISP1505. The link can optionally

assert STP to force DIR to be deasserted.

In low-power and serial modes, the link holds STP at HIGH to wake up

the ISP1505, causing the ULPI bus to return to synchronous mode.

NXT

Next: In synchronous mode, the ISP1505 drives NXT to HIGH to

throttle data. If DIR is LOW, the ISP1505 asserts NXT to notify the link

to place the next data byte on DATA[7:0] in the following clock cycle. If

DIR is HIGH, the ISP1505 asserts NXT to notify the link that a valid

USB data byte is on DATA[7:0] in the current cycle. The ISP1505 always

drives an RXCMD when DIR is HIGH and NXT is LOW, unless register

read data is to be returned to the link in the current cycle.

NXT is not used in low-power or serial mode.

Table 3.

ULPI signal description …continued

Signal

name

Direction on

ISP1505

Signal description

Table 4.

Signal mapping during low-power mode

Signal

Maps to

Direction

Description

LINESTATE0 DATA0

combinatorial LINESTATE0 directly driven by the analog receiver

LINESTATE1 DATA1

combinatorial LINESTATE1 directly driven by the analog receiver

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