EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

GENERAL DESCRIPTION

The EM84520 Scrolling Mouse Controller is specially designed to control serial mouse or PS/2 mouse device.
This single chip can interface three key-switches and 4 X-Y photo-couples plus Z-axis directly to RS-232C or
8042 controller.
There are four types Z-axis inputs used to implement scrolling mouse functionality.

FEATURES

ˇ Using 50k

1% resistor for RC oscillation.

ˇ Compatible with legacy PS/2 mouse.
ˇ Compatible with Microsoft serial scrolling mouse.
ˇ Compatible with Microsoft PS/2 scrolling mouse.
ˇ Serial or PS/2 port auto-detect.
ˇ 100 bytes PnP ID code could be filled by code layer.
ˇ Built-in noise immunity circuit.
ˇ The sampiling rate of motion detector is up to 65KHz.
ˇ Built-in three zener diodes : one in VDD to VSS, two in RTS to VDD.
ˇ CMOS push-pull RXD output.
ˇ Built-in current comparator for photo-couples input.
ˇ Built-in three step dynamic input impedance.
ˇ Three key-switches and four photo-couples inputs.
ˇ RTS debouncing circuit included.
ˇ Photo couple test mode included.
ˇ Low power dissipation.
ˇ Six types Z direction input:

1. Photo couples input. (Z/1)

4. Mechanical input. (Z/1)

2. Key-switches input.

5. Photo couples input. (Z/4)

3. Voltage-sensing input.

6. Mechanical input. (Z/2)

ˇ Package type:

EM84520AP : 16DIP, Photo couples input. (Z/1) EM84520DP: 16DIP, Mechanical input. (Z/1)
EM84520BP : 16DIP, Key-switches input.

EM84520EP : 16DIP, Photo couples input. (Z/4)

EM84520CP : 16DIP, Voltage-sensing input.

EM84520FP : 16DIP, Mechanical input. (Z/2)

APPLICATION

ˇ Serial PnP scrolling mouse.
ˇ PS/2 scrolling mouse.
ˇ Combo PnP scrolling mouse.

PIN ASSIGNMENT

OSC.OUT

CLK/RTS

DATA/RXD

OPT

VSS

OSCR

EM84520A/B/C/D/E/F

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

FUNCTIONAL BLOCK DIAGRAM

PIN DESCRIPTIONS

OPT

I/O

INPUT: 200kohm pull low to VSS.
When OPT is connected to VDD, EM84520 will enter test mode. In test mode,
L will be the output of X1,while M will be the output of X2. Toggling R key can
change these output to be Y1,Y2 or Z1,Z2 respectively.
OUTPUT: 2kHz Z-axis LED driving source with A/D/E/F version.
"1"= VDD, "0"= floating
High duty is about 60us.

OSC.OUT

The RC oscillation clock output. Or 3mA sink current output for X, Y photo
emitters.

OSCR

Connect 50k

1% precise resistor for oscillation.

CLK/RTS

I/O

Connect to 8042 auxiliary port CLK line in PS/2 mode or connect directly to RS-

232C RTS pin in serial mode. Auto-detect the operating port by this pin.

DATA/RXD

I/O

Connect to 8042 auxiliary port DATA line in PS/2 mode or connect directly to RS-

232C RXD pin in serial mode.

Three key-switches inputs. 200k

resistor pull low.

I/O

In Z-axis key mode, M key toggling can change the scrolling speed from low to

I/O

high.

Three step dynamic input impedance. If OSC.OUT is not connected to LEDs, the

dynamic input impedance will be off.

Use current comparator to measure photo-couples "ON", or "OFF".

Z-axis input.

Photo mode : Three steps dynamic input impedance. Current comparator input.
Key mode : 200 k

resistor pull low. 7 levels increased by "M" key.

Voltage mode : 200 k

resistor pull low. 7 levels voltage comparator.

Mechanical mode : 13.2k

resistor pull low. Current comparator input.

VSS

Negative power.

VDD

Power line.

Symbol

I/O

Function

Z1
Z2

OPT

OSCR

OSC.OUT

C
O

A
R
A

O
R

O
N

E
T
E
C
T

O
R

E
B

O
U
N
C

COUNTER

COMMAND

STATUS

SYSTEM CLOCK

GENERATOR

OSCILLATION

MULTIPLEXER

DATA

I/O

TIMING

CONTROLLER

COMPARATOR VOLTAGE

SENSOR

KEY-SWITCH

DETECTOR

Z-AXIS COUNTER

THREE TYPES SELECTOR

DATA/RXD

CLK/RTS

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

FUNCTION DESCRIPTIONS

(I) Serial Scrolling Mouse :

In Microsoft mode, the transmission cycle consists of four bytes in one report. Each byte contains one start
bit, 7 data bits and two stop bits. The first byte contains "L", "R" key status and four bits of the two most
significant bits in horizontal counter and vertical counter. The second byte represents the value accumulated
by horizontal counter, the third byte is the data of the vertical counter. The last byte contains "M" key status
and Z-axis value. The vertical data is transmitted in 2's complement.

Output byte arrange

Bit no.

......

1st byte

......

V7'

V6'

2nd byte

....

3rd byte

....

V5'

V4'

V3'

V2'

V1'

V0'

4th byte

....

Plug & Play ID code

When RTS input from low to high, EM84520 will send a string ID code. Customer can specify the contains
of the code area and the total lenth below 100 bytes by changing the code layer.

Field Name

Length

Field Data

Description

Other ID

<17

4D, 5A, 40, 00, 00, 00

ID for legacy

Begin ID

Begin PnP ID

PnP Revision

01, 24

Version 1.00

EISA ID

25, 2D, 23

EMC

Product ID

10, 10, 10, 11

0001

Serial Number

None provided

Class ID

<34

3C, 2D, 2F, 35, 33, 25

Mouse Class

Driver ID

<42

3C, 30, 2E, 30, 10 26, 10, 21

PnP0F0A

User Name

<42

3C, 25, 2D, 23, 00, 33, 23, 32,

EMC SCROLLING

2F, 2C, 2C, 29, 2E, 27, 00, 33,

SERIAL MOUSE

25, 32, 29, 21, 2C, 00, 2D, 2F,
35, 33, 25

Check sum

21, 15

2 bytes checks um

End PnP

End PnP ID

(II) Legacy PS/2 mouse operating:

(A) Operating mode

There are four operating modes in PS/2 mouse:
a. 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 :

(a) Send completion code AA & ID code 00.
(b) Set default :

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

sampling rate: 100 reports/s
non-autospeed
stream mode
2 dot/count
disable

b. Stream Mode:

The maximum rate of transfer is the programmed sample rate.
Data report is transmitted if
(a) switch is pressed
(b) movement has been detect

c. Remote Mode:

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

d. Wrap Mode:

Any byte of data sent by the system, except hex EC ( Reset wrap mode ) or hex FF ( Reset ), is returned
by EM84520.

B). PS/2 Mouse Data Report:

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

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

c). 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 )

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

C) PS/2 mouse Data Transmission:

a). EM84520 generates the clocking signal when sending data to and receiving data from the system.

b). The system requests EM84520 receive system data output by forcing the DATA line to an inactive level

and allowing CLK line to go to an active level.

c). Data transmission frame:

Bit

Function

Start bit ( always 0 )

2-9

Data bits ( D0 - D7 )

Parity bit ( odd parity )

Stop bit ( always 1 )

d). Data Output ( data from EM84520 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 EM84520 until CLK and DATA both high. If CLK and DATA both
are high, the transmission is ready. DATA is valid prior to the falling edge of CLK and beyond the rising edge
of CLK. During transmission, EM84520 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 EM84520
output after EM84520 has started a transmission. If this occurs before the rising edge of the tenth clock,
EM84520 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 EM84520 by holding CLK low until it can service the input
or until the system receives a request to send a response from EM84520.

e). Data Input ( from system to EM84520 ):

The system first check if EM84520 is transmitting data. If EM84520 is transmitting, the system can override
the output forcing CLK to an inactive level prior to the tenth clock. If EM84520 transmission is beyond
the tenth clock, the system receives the data. If EM84520 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, EM84520 clocks 11 bits. Following the tenth clock EM84520 checks for
an active level on the DATA line, and if found, force DATA low , and clock once more. If occurs framing
error, EM84520 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 EM84520 to response before sending its next output.

D). PS/2 Mouse Error Handling:

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

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

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

c). The counter accumulators are cleared after receiving any command except "Resend".

d). EM84520 receives a Resend command ( FE ), it transmit its last packet of data.

e). In the stream mode "Resend" is received by EM84520 following a 3-byte data packet transmission

to the system. EM84520 resend the 3-byte data packet prior to clearing the counter.

f).

A response is sent within 25 ms if

a). The system requires a response

b). An error is detected in the transmission

g). If EM84520 is in the stream mode :

a). The system disables EM84520 before issuing any command requiring a response.

b). 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 EM84520. 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

EM84520 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 Auto-speed

Reset Auto-speed

The following describes valid commands:

a). Reset ( FF )

EM84520 operation:
a). Completion the reset.
b). Transmitted FA, AA, 00 to the system.

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

c). Set default:

sampling rate: 100 reports/s
non-autospeed
stream mode
2 dots/count
disable

b). Resend ( FE )

a). Any time EM84520 receives an invalid command, it returns a Resend command to the system.
b). When EM84520 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.

c). In stream mode, if a Resend command is received by EM84520 immediately following a 3-byte data

packet transmission to the system.

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 EM84520.

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 )

EM84520 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 )

EM84520 returns to the previous mode of operation after receiving this command.

k). Read Data ( EB )

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

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 EM84520 in stream mode.

m). Status Request ( E9 )

When this command is issued by the system, EM84520 respond with a 3-byte status report as follows:

Byte

Bit

Description

1 = Right button pressed

1 = Middle button pressed

1 = Left button pressed

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 )

n). Set Resolution ( E8,XX )

EM84520 provides four resolutions selected by the second byte of this command as follows:

Second Byte XX

Resolution

8 dots/count

4 dots/count

2 dots/count

1 dot/count

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.

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

(III). Microsoft PS/2 scrolling mouse mode:

(A) Entering procedure: Except in WRAP mode, while EM84520 received the following consecutive

command.

i. F3 C8

---- set sampling rate 200/sec

ii. F3 64

---- set sampling rate 100/sec

iii. F3 50

---- set sampling rate 80/sec

(B) Operating:

a. All of the commands in legacy mode still be valid.

b. The ID code of read device type command (F2) will changed from "00" to be "03".

c. Data report will be four bytes 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 )

0-7

Z data ( D0 - D7 )

There are two ways to exit:

a. Power off.
b. Reset command (FF).

(IV). Z-axis Input Function :

(a) Photo couples input : Z-axis counter accumulates the Z1, Z2 phase changed by movement.

(b) Key-switches input : Pressing Z1, Z2 will start to fill the Z-axis counter with the value beginning at one.

Toggling "M" key can increase the value any time by one. The limit value is

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

Value

Rate per second

2.7

6.4

9.2

12.8

(d) Voltage-sensing mode : There are 7 voltage levels in Z1, Z2 input. The transmission table is the same as

key-switches mode. The relationship between the value of Z-axis counter and the voltage as folllows :

Value

Voltage

1.0V-1.6V

1.6V-2.2V

2.2V-2.8V

2.8V-3.4V

3.4V-4.0V

4.0V-4.6V

4.6V

Under V

=5V condition.

(e) Mechanical mode : The same as optical wheel mode.

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

DC ELECTRICAL CHARACTERISTICS (T

=25

C to 70

Parameters

Sym.

Min.

Typ.

Max.

Unit

X1,X2,Y1,Y2,Z1,Z2 (photo mode)

low input reference current
X1,X2,Y1,Y2,Z1,Z2 (photo mode)

106

high input reference current
X1,X2,Y1,Y2,Z1,Z2 (photo mode)

PI1

0.8

1.2

input current

(input impedance) (80

X1,X2,Y1,Y2,Z1,Z2 (photo mode)

PI2

1.5

2.1

input current

(input impedance) (500

L,M,R,OPT,Z1,Z2 (key mode)

Vail

1.5

input low voltage
L,M,R,OPT,Z1,Z2 (key mode)

Vaih

3.5

input high voltage
Z1,Z2 (voltage mode)

-0.3

+0.3

sensitivity
L,M,R,Z1,Z2 (key & voltage mode)

Imi

input current

(Vin=5V)

OPT

Ixi

-18

-56

input current
OPT

Vopt

4.5

high output current

(Iopt=20mA)

L,M,R,X1,X2,Y1,Y2,Z1,Z2

Iil

-1.0

input leakage current

(Vin=0V)

OPT

Iih

1.0

input leakage current

(Vin=5V)

OSC.OUT

Iosc

3.6

Sink current

ABSOLUTE MAXIMUM RATINGS

Parameter

Ratings

Unit

Min.

Max.

Temperature under bias

Storage temperature range

-65

150

Supply voltage

-0.3

7.5

Power dissipation

500

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

AC ELECTRICAL CHARACTERISTICS (T

=25

C to 70

* All parameters in above table are compared with VSS.

PS/2 mouse mode :

Parameters

Sym.

Min.

Typ.

Max.

Unit

Oscillating Frequency

Fosc

37.0-3%

37.0

37.0+3%

KHz

Key Debounce

Tkd

Rising Edge Crossed Width

13.5

Falling Edge Crossed Width

13.5

Mouse CLK Active Time

Tmca

40.5

Mouse CLK Inactive Time

Tmci

40.5

Time that Mouse Sample DATA from

Tmdc

13.5

CLK rising Edge
System CLK Active Time

Tsca

40.5

System CLK Inactive Time

Tsci

40.5

Time from DATA Transition to Falling Edge of CLK

Tsdc

13.5

Time from rising Edge of CLK to DATA Transition

Tscd

27.0

Time to mouse Inhibit after the 11th CLK to

Tpi

ensure mouse does not start another Transmission

PS/2 mouse mode : (T

=25

C to 70

Parameters

Sym.

Min.

Typ.

Max.

Unit

Operating voltage

4.5

5.5

Operating current

(no load)

CLK, DATA

Vt+

3.2

3.8

postive-going threshold voltage
CLK, DATA

Vt -

1.2

1.9

negative-going threshold voltage
DATA, CLK

Idc

0.56

1.86

input current

(Vin=0V )

DATA,CLK

(Iprl=-2mA)

Vprl

0.4

low output voltage

Serial mouse mode : (T

=25

C to 70

Parameters

Sym.

Min.

Typ.

Max.

Unit

Operating voltage

VDD

5.6

6.2

VRTS

12.2

Operating current

(VDD=5.4, RTS=VDD)

Iop1

Operating current

(VDD=6.2, RTS=VDD)

Iop2

RTS operating current

(VDD=5.6, RTS=11V)

Irts1

1.8

RTS operating current

(VDD=5.4, RTS=12.5V)

Irts2

RXD high output voltage

(Vrh=Vrts-2.6V)

Irh

RXD low output voltage

(Vrl=Vss+2.6V)

Irl

-2

RTS high input voltage

Vrts+

9.6

RTS low input voltage

Vrts-

6.8

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

Serial mouse mode :

Parameters

Sym.

Min.

Typ.

Max.

Unit

Oscillating Frequency

Fosc

32.4-3%

32.4

32.4+3%

KHz

Key Debounce

Tkd

Rising Edge Crossed Width

15.4

Falling Edge Crossed Width

15.4

Transmission Time

Tmx

33.33

Start bit Time

833.3

Data bit time

833.3

Stop bit Time

833.3

Mode code delay Time

Trd

X1, X2,Y1,Y2, Z1, Z2 (photo mode) 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.

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

TIMING DIAGRAM

(A) PS/2 mouse mode :

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

CLK

DATA

1st

CLK

2nd

CLK

10th

CLK

11th

CLK

Tsci

Tpi

Tscd

Tsca

Tsdc

Start

Bit

Bit0-Bit7

Parity

Bit

Stop

Bit

(A) Photo-couples pulse width

(B) Receiving Data

X1(Y1)

X2(Y2)

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

APPLICATION CIRCUIT

OSCR

CLK/R

A/RXD

OPT

OSC

.OUT

EM84520A

EM84520E

0.1

GND

+5V

CLK

50K*

5.1V

RXD

TXD

DTR

DSR

RTS

4 chips digital PT

2 chips analog PT

* 50 k

must be precise resistor under

EM84520

2-IN-ONE SCROLLING MOUSE CONTROLLER

* This specification are subject to be changed without notice.

6.28.1999

Preliminary

OSCR

CLK/R

A/RXD

OPT

OSC

.OUT

EM84520D

EM84520F

0.1

GND

+5V

CLK

50K*

RXD

TXD

DTR

DSR

RTS

COM

5.1V

4 chips digital PT

2 chips analog PT

* 50 k

must be precise resistor under

** Mechanical wheel

Part Number EM84520