FUNCTIONAL DESCRIPTION

PIN DEFINITIONS

Copyright Semtech, 1997-2001

DOC5-FJ8-DS-107

www.semtech.com

3

The UR5HCFJ8 consists functionally

of six major sections (see Functional

Diagram, previous page). These

are the Keyboard Encoder, the

Mode Control Unit, the PC

Communication Channel, the Data

Buffer, the Interrupt Control and the

8042 Emulation Channel. All

sections communicate with each

other and operate concurrently.

Mnemonic

DIP

PLCC

QFP

Type

Name and Function

VCC

40

44

38

I

Power Supply: +5V

VSS

20

22

17

I

Ground

OSCI

39

43

37

I

Oscillator input

OSCO

38

42

36

O

Oscillator output

_RESET

1

1

41

I

Reset: Apply 0V to provide orderly start-up

EKC1

37

41

35

External Keyboard Clock 1: Connects

to external keyboard Clock Line and is used

to generate an interupt for every Clock Line

transition.

VX

3

4

43

I

Tie to Vcc

VXA

3

I

Tie to Vcc

RP

6

7

2

I

Reserved: Ties to Vcc

KC

8

9

4

I/O

Keyboard Clock: Connects to PC

keyboard port clock line

KD

7

8

3

I/O

Keyboard Data: Connects to

PC port data line

EKD

10

11

6

I/O

External Keyboard Data: Connects to

external keyboard Data Lne

ECK

9

10

5

I/O

External Keyboard Clock: Connects

to external keyboard Clock Line

_IQR

2

2

42

I

Interrupt Line: Reserved for low-power

applications

R0-R5

29-34

32-37

27-32

I

Row Data Inputs

R6

5

6

1

I

R7

36

39

34

I

C0-C7

12-19

13-17

8-15

O

Column Select Outputs: Selects 1 of

19-21

O

16 columns

C8-C15

28-21

31-24

26-23

O

21-18

O

CL

11

12

7

O

Caps Lock LED

NL

4

5

44

O

Num Lock LED

SL

35

38

33

O

Scroll Lock LED

NC

18

16,22

No Connects: These pins are unused.

23,40

39,40

Note: An underscore before a pin mnemonic denotes an active low signal.

KEYBOARD ENCODER

The controller continuously scans a

keyboard organized as an 8 row by

16 column matrix for a maximum of

128 keys. Smaller-size keyboards

are supported provided that all

unused row lines are pulled to Vcc.

The IC selects 1 of the 16 column

lines (C0-C15) every 512 mS and

then reads the row data lines (R0-

R7). A key closure is detected as a

0 in the corresponding position of

the matrix. A complete scan cycle

for the entire keyboard takes

approximately 9.2 mS. Each key

found pressed is debounced for a

period of 20 mS. Once the key is

verified, the corresponding key

code(s) are loaded into the transmit

buffer of the PC Communication

Channel.

Switch Matrix Encoding

Each matrix location is programmed

to represent either a single key or a

key combination of the IBM 101/102

standard keyboard.

Scan Code Table Sets

The UR5HCFJ8 supports all three

scan code table sets. Scan Code

Sets 1 and 2 are the default sets for

AT/PS/2 systems. Scan Code Table

Set 3 allows the user to program

individual key attributes such as

Make/Break and Typematic or

Single-Touch Action. For more

information, refer to the IBM

Technical Reference Manuals.