PS/2 PORTS

Copyright ©1998-2001 Semtech Corporation

DOC8-007-001-DS-108

www.semtech.com

11

The Juno™ implements the

Semtech-patented "Message loss-

less wake-up™" method to operate

all three PS/2 ports. This method

enables the controller to interface

with devices attached to its PS/2

ports while still operating in the

"Stop" mode. Typical power

consumption of the PS/2 ports is

therefore 1 µA.

If a PS/2 device reports a data

packet, the controller will exit the

"Stop" mode for as long as it takes

to process the device message and

relay the information, if necessary,

to the Host system. This operation

is done transparently to the Host,

without any message loss or any

response delays from the input

devices.

This unique technology allows

computers to operate at their

minimum power consumption state

even with PS/2 devices attached.

Systems that employ an internal

pointing device, such as a touch

pad or a force stick, can benefit the

most from this feature, since the

pointing device will force the

controller to exit its "Stop" mode only

when there is data to be reported.

The UR8HC007-001 provides three PS/2 ports for the hot-plug connection of

an external keyboard, an external mouse and an internal mouse.

All of the internal and external devices are active at all times. Data from

both the external and internal keyboards and mice are merged and

seamlessly presented to the system.

5-Volt Tolerant PS/2 ports

The UR8HC007 controller can be powered by a power supply between 3

and 5 Volts (+/- 10%). Even when the USAR controller is powered by a 3-

Volt supply, the three PS/2 ports can directly interface with 5-Volt powered

devices — without the need of any external level-shifting circuitry. The Host

can enable or disable all the external PS/2 ports simultaneously, in sync with

the 5-Volt power plane that powers them. Alternatively, it can select any

PS/2 port selectively, through the "HID enable/disable control" register.

PS/2 Mouse Handling

This port supports MouseWheel functionality.

An internal mouse connected to a system’s PS/2 port consumes a significant

amount of power as it must always be “on.” A mouse connected to one of

Juno’s™ PS/2 ports consumes minimal power because the Juno™ will

power down even when the internal mouse is connected and active.