EM84510

PS/2 SCROLLING MOUSE CONTROLLER

4

* This specification are subject to be changed without notice.

5.30.2001

C) PS/2 mouse Data Transmission:

i). EM84510 generates the clocking signal when sending data to and receiving data from the system.

ii). The system requests EM84510 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:

Bit

Function

1

Start bit ( always 0 )

2-9

Data bits ( D0 - D7 )

10

Parity bit ( odd parity )

11

Stop bit ( always 1 )

iv). Data Output ( data from EM84510 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 EM84510 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, EM84510 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 EM84510

output after EM84510 has started a transmission. If this occurs before the rising edge of the tenth clock,

EM84510 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 EM84510 by holding CLK low until it can service the input

or until the system receives a request to send a response from EM84510.

v). Data Input ( from system to EM84510 ):

System first check if EM84510 is transmitting data. If EM84510 is transmitting, the system can override

the output forcing CLK to an inactive level prior to the tenth clock. If EM84510 transmission is beyond

the tenth clock, the system receives the data. If EM84510 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

µ 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, EM84510 clocks 11 bits. Following the tenth clock EM84510 checks for

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

error, EM84510 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 EM84510 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.