UR5HCFJL Datasheet, PDF (5/20 Pages) Semtech Corporation – Zero-PowerTM Keyboard Encoder for Portable Systems

8042 EMULATION CHANNEL
The GreenCoder^TM fully emulates a
system’s keyboard port, available to
a standard 84/85/101/102 external
keyboard or other 8042-compatible
device. Communication with a
keyboard-compatible device is
accomplished by clock and data
lines via EKC and EKD pins,
respectively. A third pin, EKC1 that
connects to the Clock Line,
interrupts the controller whenever
the external device initiates a
communication session.
When power is first applied, the
controller proceeds with the
standard reset sequence with the
external device. Data and
commands initiated from the
external device are buffered in the
controller’s FIFO along with data
from the scanned matrix, and then
are presented to the system as if
they were coming from a single
source. Once they are
acknowledged, commands and
data from the system are then
transmitted to the external device.
SPECIAL HANDLING
Connection of External Device
The UR5HCFJL will detect the presence of an external device. If an
external keyboard or other device was not connected during power-on and
is connected at a later time, the encoder will proceed with the normal reset
routine in order to properly initialize the external device. After
communication has been established, the encoder will continue to check for
the presence of the external device. While the external device is
connected, the encoder will not enter the sleep mode. If the device is
disconnected at a later time, the encoder will become aware of it. If a
subsequent connection takes place, the controller will re-initiate a reset
sequence. This unique feature allows the user to connect or disconnect an
external device at any time without having to reset the system.
Shift Status LEDs
Shift Status LEDs (Num Lock, Caps Lock and Scroll Lock) indicate the
status of the system and are controlled by commands sent from the system.
Set/Reset Status Indicator Commands from the system will be executed
both by the external keyboard and the scanned matrix.
For example, if the user presses the Caps Lock Key on either keyboard, the
Caps Lock LED will be affected on both keyboards. The LED status
indicators are properly set after each new connection of an external
keyboard.
Copyright Semtech, 1997-2001
5
DOC5-FJL-DS-106
www.semtech.com