Serial Mouse Specification

Pin-out Description and Protocol Summary

RS-232 Cable Terminations and Electrical Data Interface
(DB-9 Female Connector)

Pin # Code Description MOUSE-TRAK Utilization
1 DCD Data Carrier Detect No Connection
2 RXD Receive Data See Protocol Summary
3 TXD Transmit Data Must remain low, <= –5V
4 DTR Data Terminal Ready See Protocol Summary
5 GND Signal Ground Ground
6 DSR Data Set Ready No Connection
7 RTS Request to Send See Protocol Summary
8 CTS Clear to Send No Connection
9 RI Ring Indicator No Connection

Serial Mouse Protocols Summary

  Mouse Systems 5-byte Microsoft Serial 3-byte
RXD
Byte # Data Interpretation
1: 1 0 0 0 L M R (bit assignments)
2: X signed movement
3: Y signed movement
4: X signed movement since byte 2
5: Y signed movement since byte 3
L = Left button
M = Middle button
R = Right button
L/M/R Button Up = 1
L/M/R Button Down = 0
X = right - left
Y = up - down
Byte # Bit Assignments
1: 1 L R Y7 Y6 X7 X6
2: 0 X5 X4 X3 X2 X1 X0
3: 0 Y5 Y4 Y3 Y2 Y1 Y0
L = Left button
R = Right button
Button Up = 0
Button Down = 1
X7 -> X0 = Bit positions of signed X
movement since last report.
Y7 -> Y0 = Bit positions of signed Y
movement since last report.
X0 & Y0 = least significant bits.
X = right - left
Y = down - up
DTR Note: MUST be the same as RTS.
Low, <= –5V or lower, OR
High, >= +5V or higher AND J1 removed.
(J1 is accessible through hole in case bottom) 		Note: MUST be the same as RTS.
High, >= +5V or higher.
RTS Note: MUST be the same as DTR.
Low, <= –5V or lower, OR
High, >= +5V or higher AND J1 removed.
(J1 is accessible through hole in case bottom) 		Note: MUST be the same as DTR.
High, >= +5V or higher.
Data Rate 1200 baud (bits per second) 1200 baud (bits per second)
Parity Bits None None
Data Bits 8 7
Stop Bits 1 1