/home/techdatasheets.com/WWW/datasheets_html/320811/datasheet-EM84502BM

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

EM84502

PS/2 MOUSE CONTROLLER

GENERAL DESCRIPTION

The EM84502 Mouse Controller is specially designed to control PS/2 mouse device.This single chip can

interface three key-switches and four photo-couples direct to 8042. EM84502 can receive command and echo

status or data format which are compatible with IBM PS/2 mode mouse. Key debouncing circuit is provided

to prevent false entry and improve the accuracy.

In the conventional mouse, a great number of noises are generated when the grid is partially closed or opened.

These noise are usually mistaken for movement signals by conventional mouse controller and the cursor of the

dispaly screen is thus moved frequently up and down or back and forth. This will consumes a great amount of

energy.The EM84502 PS/2 mouse controller provides noise immunity circuits to eliminate these noise

in order to reduce energy consumption.

FEATURES

• Being compatiable with PS/2 mouse mode.

• Built-in noise immunity circuit.

• Low power dissipation.

• RC oscillation.

• Three key-switches and four photo-couples inputs.

• Both key-press and key-release debounce interval 12 ms.

• Through three key-switches input, EM84502 can exert seven different output.

• The motion detector of the EM84502 could sense 8 m/sec maximun with 200 DPI wheels.

APPLICATIONS

• Optical mouse or pen-mouse.

• Mechanical mouse or pen-mouse.

• Optomechanical mouse or pen-mouse.

• Mechanical track ball.

• Optomechanical track ball.

PIN ASSIGNMENT

* (Under developed)

OSC.OUT

CLK

DATA

VSS

OSCR

EM84502BP

OSC.OUT

CLK

DATA

VSS

OSCR

EM84502BM*

OSC.OUT

CLK

DATA

VSS

OSCR

EM84502AP

OSC.OUT

CLK

DATA

VSS

OSCR

EM84502AM

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

Power

X, Y inputs.

Floating : Comparator input.

GND : Schmitt trigger input.

Short to OSC OUT : Testing Mode.

OSCOUT

Clock output.

CLK

I/O

8042 auxiliary port CLK line.

DATA

I/O

8042 auxiliary port DATA line.

Ground

Three key-switches exert seven different combinations totally. Both key-pressed

and key-released signals will be sent accomplanied with horizontal and vertical

state. The status of the key-switches will be preserved, whenever the value of

horizontal or vertical counters will present at DATA. And the debounce interval

for both key-press and key-release is 12 ms.

Four photo-couple signals denote UP, DOWN, LEFT, and RIGHT state.

During the scaning period, as long as the photo-couples change their states, the

value of vertical or horizontal counter will increase or decrease accordingly.

OSCR

30 Kohm

5% pull low for 35 KHz oscillation.

FUNCTION DESCRIPTIONS

A) Operating mode

There are four operating modes in PS/2 mouse:

i). Reset Mode:

In this mode a self-test is initiated during power-on or by a Reset command. After reset signal, PS/2

mouse will send:

1). Completion code AA & ID code 00.

FUNCTIONAL BLOCK DIAGRAM

COUNTER

TIMING

CONTROLLER

DATA

I/O

SYSTEM

CLOCK

GENERATOR

OSCR

OSC OUT

DATA

CLK

Symbol

I/O

Function

PIN DESCRIPTIONS

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

2). Set default:

sampling rate: 100 reports/s

non-autospeed

stream mode

2 dot/count

disable

ii). Stream Mode:

The maximum rate of transfer is the programmed sample rate.

Data report is transmitted if

1). switch is pressed

2). movement has been detect

iii). Remote Mode:

Data is transmitted only in response to a Read Data command.

iv). Wrap Mode:

Any byte of data sent by the system, except hex EC ( Reset wrap mode ) or hex FF ( Reset ), is returned

by EM84502.

B). PS/2 Mouse Data Report:

i).

In stream mode: A data report is sent at the end of a sample interval.

ii). In remote mode: A data report is sent in response to Read Data command.

iii). Data report format:

Byte

Bit

Description

Left button status; 1 = pressed

Right button status; 1 = pressed

Middle button status; 1 = pressed

Reserve

X data sign; 1 = negative

Y data sign; 1 = negative

X data overflow; 1 = overflow

Y data overflow; 1 = overflow

0-7

X data ( D0 - D7 )

0-7

Y data ( D0 - D7 )

C) PS/2 mouse Data Transmission:

i). EM84502 generates the clocking signal when sending data to and receiving data from the system.

ii). The system requests EM84502 receive system data output by forcing the DATA line to an inactive

level and allowing CLK line to go to an active level.

iii). Data transmission frame:

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

Bit

Function

Start bit ( always 0 )

2-9

Data bits ( D0 - D7 )

Parity bit ( odd parity )

Stop bit ( always 1 )

iv). Data Output ( data from EM84502 to system ):

If CLK is low ( inhibit status ) , data is no transmission.

If CLK is high and DATA is low ( request-to-send ), data is updated. Data is received from the system

and no transmission are started by EM84502 until CLK and DATA both high. If CLK and DATA are both

high, the transmission is ready. DATA is valid prior to the falling edge of CLK and beyond the rising edge

of CLK. During transmission, EM84502 check for line contention by checking for an inactive level on CLK

at intervals not to exceed 100u sec. Contention occurs when the system lowers CLK to inhibit EM84502

output after EM84502 has started a transmission. If this occurs before the rising edge of the tenth clock,

EM84502 internal store its data in its buffer and returns DATA and CLK to an active level. If the contention

does not occur by the tenth clock, the transmission is complete.

Following a transmission, the system inhibits EM84502 by holding CLK low until it can service the input

or until the system receives a request to send a response from EM84502.

v). Data Input ( from system to EM84502 ):

System first check if EM84502 is transmitting data. If EM84502 is transmitting, the system can override

the output forcing CLK to an inactive level prior to the tenth clock. If EM84502 transmission is beyond

the tenth clock, the system receives the data. If EM84502 is not transmitting or if the system choose to

override the output, the system force CLK to an inactive level for a period of not less than 100

sec while

preparing for output. When the system is ready to output start bit (0), it allows CLK go to active level. If

request-to-send is detected, EM84502 clocks 11 bits. Following the tenth clock EM84502 checks for

an active level on the DATA line, and if found, force DATA low , and clock once more. If occurs framing

error, EM84502 continue to clock until DATA is high, then clocks the line control bit and request a

Resend. When the system sends out a command or data transmission that requires a response, the system

waits for EM84502 to response before sending its next output.

D). PS/2 Mouse Error Handling:

i).

A Resend command ( FE ) following receipt of an invalid input or any input with incorrect parity.

ii). If two invalid input are received in succession, an error code of hex FC send to the system.

iii). The counter accumulators are cleared after receiving any command except “Resend”.

iv). EM84501 receives a Resend command ( FE ), it transmit its last packet of data.

v). In the stream mode “Resend” is received by EM84502 following a 3-byte data packet transmission

to the system. EM84502 resend the 3-byte data packet prior to clearing the counter.

vi). A response is sent within 25 ms if

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

a). The system requires a response

b). An error is detected in the transmission

vii). When a command requiring a response is issued by the system ,another command should not be issue

until either the response is received or 25ms has passed.

E). PS/2 Mouse Commands Description:

There are 16 valid commands that transmits between the system and EM84502. The “FA” code is always the

first response to any valid input received from the system other than a Set Wrap Mode or Resend command.

The following table list the commands:

Hex Code Command

EM84502 echo code

Reset

FA,AA,00

Resend

XX,(XX,XX)

Set Default

Disable

Enable

F3,XX

Set Sampling Rate

FA,FA

Read Device Type

FA,00

Set Remote Mode

Set Wrap Mode

Reset Wrap Mode

Read Data

FA,XX,XX,XX

Set Stream Mode

Status Request

FA,XX,XX,XX

E8,XX

Set Resolution

FA,FA

Set Autospeed

Reset Autospeed

The following describes valid commands:

a). Reset ( FF )

EM84502 operation:

i). Completion the reset.

ii). Transmitted FA,AA,00 to the system.

iii). Set default:

sampling rate: 100 reports/s

non-autospeed

stream mode

2 dots/count

disable

b). Resend ( FE )

i). Any time EM84502 receives an invalid command, it returns a Resend command to the system.

ii). When EM84502 receives a Resend command, it retransmits its last packet of data. If the last packet was

a Resend command, it transmits the packet just prior to the Resend command.

iii). In stream mode, if a Resend command is received by EM84502 immediately following a 3-byte data

packet transmission to the system.

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

c). Set Default ( F6 )

The command reinitializes all conditions to the power-on defaults.

d). Disable ( F5 )

This command is used in the stream mode to stop transmissions from EM84502.

e). Enable ( F4 )

Begins transmissions, if in stream mode.

f). Set Sampling Rate ( F3,XX )

In the stream mode, this command sets the sampling rate to the value indicated by byte hex XX,

shown in following:

Second byte XX

Sample Rate

10/sec

20/sec

40/sec

60/sec

80/sec

100/sec

200/sec

g). Read Device Type ( F2 )

EM84502 always echoes “ FA,00 “ following this command.

h). Set Remote Mode ( F0 )

Data value are reported only in response to a Read Data command.

i). Set Wrap Mode ( EE )

Wrap mode remains until Reset ( FF ) or Reset Wrap Mode( EC ) is received.

j). Reset Wrap Mode ( EC )

EM84502 returns to the previous mode of operation after receiving this command.

k). Read Data ( EB )

This command is executed in either remote or stream mode. The data is transmitted even if there has been

no movement since the last report or the button status is unchanged. Following a Read Data command,

the registers are cleared after a data transmission.

l). Set Stream Mode ( EA )

This command sets EM84502 in stream mode.

m). Status Request ( E9 )

When this command is issued by the system, EM84502 respond with a 3-byte status report as follows:

Byte

Bit

Description

1 = Right button pressed

1 = Middle button pressed

1 = Left button pressed

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

n). Set Resolution ( E8,XX )

EM84502 provides four resolutions selected by the second byte of this command as follows:

Second Byte XX

Resolution

8 dot/count

4 dot/count

2 dot/count

1 dot/count

Reserved

0 = Normal speed, 1 = Autospeed

0 = Disabled, 1 = Enabled

0 = Stream mode, 1 = Remote mode

Reserved

0-7

Current resolution setting ( D0 - D7 )

0-7

Current sampling rate ( D0 - D7 )

o). Set Autospeed ( E7 )

At the end of a sample interval in the stream mode, the current X and Y data values are converted new values.

The sign bits are not involved in this conversion. The conversion is only in stream mode. The relationship

between the input and output count follows:

Input

Ouput

≥

6 )

2.0*N

p). Reset Autospeed ( E6 )

This command restore normal speed.

F) Testing mode

Whenever OPT is connected to OSC OUT, the chip will enter buyer's testing mode. The X direction output

signals of comparators will present to L and M pin. Pressing "R" key can toggle the output from X direction

to Y direction.

ABSOLUTE MAXIMUM RATINGS

Parameter

Sym.

Ratings

Unit

Temperature under bias

OPR

0~70

Storage temperature range

STR

-65~150

Input voltage

-0.3~6.0

Output voltage

-0.3~6.0

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

* All voltages in above table are compared with V

* All parameters in above table are tested under V

=5V.

* CLK & DATA output gates are open drains that connect to pull up resistors.

* X1, X2,Y1,T2 Input Impedance

5.0

4.0

3.0

2.0

1.0

10.0M

1.0K

2.0K

3.0K

4.0K

5.0K

6.0K

7.0K

8.0K

9.0K

10.0.K

11.0K

12.0K

13.0K

14.0K

VOLTS (LIN)

15.0K

16.0K

MAX.

TYP.

MIN.

DC ELECTRICAL CHARACTERISTICS (T

=25

C to 70

Parameters

Sym.

Min.

Typ.

Max.

Unit

Operating voltage

4.5

5.5

Operating current

(no load)

1.2

X,X2,Y1,Y2 low input reference current

X,X2,Y1,Y2 high input reference current

106

X,X2,Y1,Y2 input current

0.8

1.2

Schmitt trigger input

(76

X,X2,Y1,Y2 input current

0.8

1.2

Comparator input

(80

X,X2,Y1,Y2 input current

1.5

2.1

Comparator input

(500

CLK, DATA postive-going

Vt+

3.2

3.8

threshold voltage

CLK, DATA negative-going

Vt -

1.2

1.9

threshold voltage

Low input voltage, other pins

Vail

1.5

High input voltage, other pins

Vaih

3.5

L, M, R input current

Imi

16.6

(pull low resistor Vin=5V)

PS/2 mouse mode DATA, CLK input Current

Idc

0.56

1.86

(pull up resistor)

(VIN=0V)

PS/2 mouse mode DATA, CLK low output voltage

Vprl

0.4

(Iprl=-2mA)

L, M, R, X1, X2, Y1, Y2 input leakage current

Iil

1.0

(Vin=0V)

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

TIMING DIAGRAM

(1) Photo-couples pulse width :

AC ELECTRICAL CHARACTERISTICS (T

C to 70

Parameters

Sym.

Min.

Typ.

Max.

Unit

Oscillating Frequency

Fosc

37.5-10%

37.5

37.5+10%

KHz

Key Debounce

Tkd

Rising Edge Crossed Width Fosc=35 KHz

14.3

Falling Edge Crossed Width Fosc=35 KHz

14.3

Mouse CLK Active Time

Tmca

42.9

Mouse CLK Inactive Time

Tmci

42.9

Mouse Sample DATA from

Tmdc

14.3

CLK rising Edge

System CLK Active Time

Tsca

42.9

System CLK Inactive Time

Tsci

42.9

Time from DATA Transition to Falling Edge of CLK

Tsdc

14.3

Time from rising Edge of CLK to DATA Transition

Tscd

28.6

Time to mouse Inhibit after the 11th CLK to

Tpi

ensure mouse does not start another Transmission

PS. The AC timings are measured under using 35 KHz system clock signal.

(2) PS/2 Mouse

(A) Receiving DATA

X1 (Y1)

X2 (Y2)

• • • • •

• • • • • • • • • • • •

• • • • •

• •

CLK

DATA

Inhibit

1st

CLK

2nd

CLK

9th

CLK

10th

CLK

11th

CLK

Tmca

Tmci

Tmdc

Start

Bit

Bit0 -Bit7

Parity

Bit

Stop

Bit

Line

Control

Bit

EM84502

PS/2 MOUSE CONTROLLER

* This specification are subject to be changed without notice.

8.3.2001

(B) Sending DATA

• • • • • • • • • • •

• • • • • • • • • • • •

• • • • •

CLK

DATA

1st

CLK

2nd

CLK

10th

CLK

11th

CLK

Tsci

Tsca

Tscd

Start

Bit

Bit0 -Bit7

Parity

Bit

Stop

Bit

Tsdc

Tpi

• • • • • • • • •

(R,M,L)

INTERNAL SIGNAL

DATA INPUT SIGNAL

DATA OUTPUT SIGNAL

PS2 MOUSE ENABLE

DATA

CLK

CLK INPUT SIGNAL

CLK OUTPUT SIGNAL

PS2 MOUSE ENABLE

AC Timing point:

EM84502 I/O pin equivalent circuit :

R,M,L :

DATA :

CLK :

X1,X2,Y1,Y2 :

48.4

39.6

Output:

Input:

X1,X2,Y1,Y2 PIN

L,M,R PIN

-0.8

+0.8

CLK, DATA PIN

-2.6

+0.4

DATA,

CLK PIN (PS/2 mouse mode)

+1.6V

PHASE DIGITAL SIGNAL

X1,X2,Y1,Y2

12.5K

80µA

30K

12.5K

13.2K