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The block diagram below shows the receiver section with the U1 and U2 chips.

Infrared receiver 

Serial mouse

U1 & U2 interface

PS/2 mouse

Mac mouse

98 bus mouse

IC2007

U1

(IX2955CE)

IC2008

U2

(IX2956CE)
(IX3015CE)

Remarks: The U1 and U2 chips are linked using special interface signal lines

(ACK, DAT, CLK, BUTTON and SLEEP).

Pin

Function

1

NC

2

NC

3

NC

4

Serial mouse output

5

Power (VCC)

6

Oscillator input (Xtal 2)

7

Oscillator output (Xtal 1)

8

Input from infrared receiver

9

Serial mouse switching input

10

ACK input from U2

11

NC

12

NC

13

NC

14

Ground (GND)

15

DAT output to U2

16

CLK output to U2

17

SLEEP output to U2

18

BUTTON output to U2

Pin

Function

1

Output of 98 bus mouse’s right button

2

Output of 98 bus mouse’s left button

3

SLEEP input from U1

4

NC

5

NC

6

NC

7

NC

8

Power (VCC)

9

NC

10

Oscillator input (Xtal 1)

11

Mac ADB mouse input

12

PS-2/Mac mouse switching input

13

AT/98 mode switching input (Mode select)

14

98 bus mouse XA output

15

98 bus mouse XB output

16

98 bus mouse YA output

17

98 bus mouse YB output

18

98 bus mouse speed switching input (98 SPEED)

19

DAT input from U1

20

CLK input from U1

21

BUTTON input from U1

22

Ground (GND)

23

NC

24

PS-2 mouse data line

25

PS-2 clock line

26

ACK output to U1

27

Mac ADB mouse output

28

NC

When the serial mouse switching input (pin (9) of U1) is at high level, the serial mouse data is given out of the U1.
When at low level, the mouse connected with the U2 works.

When the PS-2/Mac mode switching input (pin (12) of U2) is at low level, the PS-2 mode is called. When at high
level, the Mac mode is called.

When the AT/98 mode switching input (pin (13) of U2) is at lowlevel, the PS-2 mouse or the Mac mouse works.
When at high level, the 98 bus mouse works.

When the 98 bus mouse speed switching input (pin (18) of U2) is at low level, the cursor speed decreases.
When at high level, the mouse speed increases.

The connection for each mouse interface is referred to in the relevant circuit diagrams.

(a) Basic specifications

Compatible PC

: PC/AT compatible (DOS/V), Toshiba J3100, AX computers

Port used

: COM1 or COM2

Data format

: Microsoft compatible

Transfer format

: 1 start bit, 7 data bits, 1 stop bit, non-parity

Data transfer rate : Fixed at 1200 bps
Mouse power*

: 5V power from RTS and DTR lines

* : The mouse itself does not have the +12V power required for usual RS-232-C interfaces. The RTS and DTR

signal lines are used for 5V power for the mouse logic. the TX signal line (-10V) is also employed in order to
keep the mouse output at the +5V level.

(b) Data format

The table below lists the 3-byte transfer data format for the serial mouse.

Byte

Bit

Explanation

1

6

Always at “1”

5

Left button (ON at “1”)

4

Right button (ON at “1”)

3

Y7

2

Y6

1

X7

0

X6

2

6

Always at “0”

5

X5

4

X4

3

X3

2

X2

1

X1

0

X0

3

6

Always at “0”

5

Y5

4

Y4

3

Y3

2

Y2

1

Y1

0

Y0

(c) Transfer format

Shown below is the 1-byte transfer format for the serial mouse

The 3-byte data transfer is made in the following manner.

SOUT

SOUT

Tbh

Tb1

Tb1, Tbh : 0.833 msec

Tdc : 33.3 mesc
Td

: 22.5 msec

Tdc

Td

D1

1st

2nd

3rd

1st

2nd

3rd

Start

bit

Stop

bit

D2

D3

D4

D5

D6

In the above figure, Tdc is the data sampling period, during which the mouse gives out the serial data to the host
computer. This means that data acquisition at the mouse (A/D conversion. for example) is done during this time.

(d) Interface start sequence

When the mouse driver of the computer gets started, the serial port of the computer is initialized and the RTS
and DTR lines are given about +8V. At this point, the MCU at the mouse gets started and gives out the character
code “M” of the serial data to the computer that is waiting for this code for a certain period of time. In so doing,
the mouse driver of the computer recognizes that a Microsoft-compatible serial mouse is hooked up.

(a) Basic specifications

Compatible PC

: PC/AT compatible (DOS/V), Toshiba J3100, AX computers

Port used

: PS-2 mouse port

Data format

: IBM PS-2 mouse compatible

Transfer format

: 1 start bit, 8 data bits, 1 stop bit, odd parity, sync communication

Data transfer rate : About 10 kbps
Mouse power

: +5V power supplied from computer

(b) Data format

Communication between the host computer and the mouse is made using the following 17 commands via the
PS-2 mouse interface.

Code (hex)

Function

FF

Reset

FE

 Resend

F6

Set default

F5

Disable

F3

Enable

F3

Set sampling rate

F2

Read device type

F0

Set remote mode

EE

Set lap mode

EC

Reset lap mode

EB

Read data

EA

Set stream mode

E9

Status request

E8

Set resolution

E7

Set scaling

E6

Reset scaling

FA

Acknowledge

Byte

Bit

Explanation

1

7

Y data overflow (overflow at “1”)

6

X data overflow (overflow at “1”)

5

Y data code (negative at “1”)

4

X data code (negative at “1”)

3

Reserved (1)

2

Reserved (0)

1

Right button status (ON at “1”)

0

Left button status (ON at “1”)

2

7-0

X data

3

7-0

Y data

The table below lists the data report format with respect to the read data.