Silan

Semiconductors

SC84520

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

Rev: 1.0

2000.12.31

9

SC84520 has started a transmission. If this occurs before the rising edge of the tenth clock, SC84520 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.

e. Data Input (from system to SC84520):

The system first check if SC84520 is transmitting data. If SC84520 is transmitting, the system can override the

output forcing CLK to an inactive level prior to the tenth clock. If SC84520 transmission is beyond the tenth

clock, the system receives the data. If SC84520 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

µs 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,

SC84520 clocks 11 bits, Following the tenth clock SC84520 checks for an active level on the DATA line, and if

found, force DATA low, and clock once more. If occurs framing error, SC84520 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 SC84520 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.

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

d. SC84520 receives a Resend command (FE), it transmit its last packet of data.

e. In the stream mode “Resend” is received by SC84520 following a 3-byte data packet transmission to the

system. SC84520 resend the 3-byte data packet prior to clearing the counter.

f. A response is sent within 25ms if

a) The system requires a response

b) An error is detected in the transmission

g. If SC84520 is in the stream mode:

a) The system disables SC84520 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 SC84520. 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: