X76F200

3

Figure 1. X76F200 Device Operation

Retry Counter

The X76F200 contains a retry counter. The retry counter

allows 8 accesses with an invalid password before any

action is taken. The counter will increment with any

combination of incorrect passwords. If the retry counter

overflows, the memory area and both of the passwords are

cleared to "0". If a correct password is received prior

to retry counter overflow, the retry counter is reset and

access is granted.

Device Protocol

The X76F200 supports a bidirectional bus oriented

protocol. The protocol defines any device that sends data

onto the bus as a transmitter and the receiving device as a

receiver. The device controlling the transfer is a master

and the device being controlled is the slave. The master will

always initiate data transfers and provide the clock for

both transmit and receive operations. Therefore, the

X76F200 will be considered a slave in all applications.

Clock and Data Conventions

Data states on the SDA line can change only during SCL

LOW. SDA changes during SCL HIGH are reserved for

indicating start and stop conditions. Refer to Figure 2 and

Figure 3.

Start Condition

All commands are preceded by the start condition, which

is a HIGH to LOW transition of SDA when SCL is

HIGH. The X76F200 continuously monitors the SDA and SCL

lines for the start condition and will not respond to

any command until this condition is met.

A start may be issued to terminate the input of a control byte or

the input data to be written. This will reset the

device and leave it ready to begin a new read or write command.

Because of the push/pull output, a start

cannot be generated while the part is outputting data.

Starts are inhibited while a write is in progress.

Stop Condition

All communications must be terminated by a stop

condition. The stop condition is a LOW to HIGH transition

of SDA when SCL is HIGH. The stop condition is also used

to reset the device during a command or data input

sequence and will leave the device in the standby power

mode. As with starts, stops are inhibited when outputting

data and while a write is in progress.

Acknowledge

Acknowledge is a software convention used to indicate

successful data transfer. The transmitting device, either

master or slave, will release the bus after transmitting eight

bits. During the ninth clock cycle the receiver will

pull the SDA line LOW to acknowledge that it received the

eight bits of data.

The X76F200 will respond with an acknowledge after

recognition of a start condition and its slave address. If

both the device and a write condition have been

selected, the X76F200 will respond with an acknowledge

after the receipt of each subsequent eight-bit word.

LOAD COMMAND/ADDRESS BYTE

LOAD 8-BYTE

PASSWORD

VERIFY PASSWORD

ACCEPTANCE BY

USE OF ACK POLLING

READ/WRITE

DATA

BYTES