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UR5HCFJ8-FB

Low-Power Keyboard Encoder for Portable Systems

Semtech Corporation 

SPECIAL HANDLING

Hot Plug-Ins of External

Device

The UR5HCFJ8 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 keyboard. After

communication has been

established, the encoder will

continue to check for the presence

of the external keyboard. 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 reinitiate 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 in both

keyboards. The LED status

indicators are properly set after

every new connection of an external

keyboard.

PC COMMUNICATION

The UR5HCFJ8 implements all the

standard functions of

communication with a BIOS-

compatible PC/XT or AT/PS/2 host

system. Two lines, KC and KD,

provide bi-directional clock and

data signals. In addition, the

UR5HCFJ8 supports all commands

from and to the system, as

described in the IBM Technical

Reference Manuals.

The following table shows the

commands that the system may

send and their values in hex.

Command

Hex Value

Set/Reset Status

ED

Indicators

Echo

EE

Invalid Command

EF

Select Alternate

F0

Scan Codes

Invalid Command

F1

Read ID

F2

Set Typematic

F3

Rate/Delay

Enable

F4

Default Disable

F5

Set Default

F6

Set All Keys

Typematic

F7

Make/Break

F8

Make

F9

Typematic/Make/Break

FA

Set Key Type

Typematic

FB

Make/Break

FC

Make

FD

Resend

FE

Reset

FF

Table 2: Keyboard Commands from the

System (AT/PS/2 protocol)

These commands are supported in

the AT/PS/2 protocol and can be

sent to the keyboard at any

time.The following table shows the

commands that the keyboard may

send to the system.

Command

Hex Value

Key Detection

00*

Error/Overrun

Keyboard ID

83AB

BAT Completion Code

AA

BAT Failure Code

FC

Echo

EE

Acknowledge (Ack)

FA

Resend

FE

Key Detection

Error/Overrun

FF**

*Code Sets 2 and 3

**Code Set 1

Table 3: Keyboard Commands to the

System (AT/PS/2 protocol)

8042 Emulation Channel

The UR5HCFJ8 fully emulates a

system’s keyboard port, available to

a standard 82/101/102 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,

connects to the Clock Line and

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. After they are

acknowledged, commands and

data from the system are

transmitted to the external device.

Copyright Semtech, 1997-2001

5

DOC5-FJ8-DS-107

www.semtech.com

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