X46402

Preliminary Information

9

Figure 9. Definition of Start and Stop Conditions

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 X46402 will respond with an acknowledge after rec-

ognition of a start condition and its slave address. If both

the device and a write condition have been selected, the

X46402 will respond with an acknowledge after the

receipt of each subsequent eight-bit word.

Read Device ID Command

A special, non-password protected command reads the

device ID. The device ID is a 32 bit identification code

that can be generic or tailored to the needs of an individ-

ual company. The last of the 32 bits indicates whether

the device has been tampered with by an unauthorized

user attempting to enter invalid passwords.

Reset Device Command

The Reset Device command resets the tamper bit, clears

the tamper counter and removes the tamper “lock”

(allowing the device to accept commands). However, the

Reset Device command does not clear any memory

array area.

SCL

SDA

Start Condition

Stop Condition

Table 3. X46402 Instruction Set

Notes: Illegal command codes will be disregarded. The part will respond with a “no-ACK” to the illegal byte and then return to the standby mode.

1st Byte

after Start

1st Byte

after

Password

2nd Byte

after

Password

Command Description

Password used

1000 0000

High Address

Low address

Password Memory Array Read

Memory Read

1000 1000

High Address

Low address

OTP Read

OTP Read

1001 0000

High Address

Low address

Password Memory Array Write

Memory Write

1001 1000

High Address

Low address

OTP Write

OTP Write

1010 0000

0000 0000

0000 0000

Change Memory Read Password

Memory Read

1010 1000

0000 0000

0000 0000

Change OTP Read Password

OTP Read

1011 0000

0000 0000

0000 0000

Change Memory Write Password

Memory Write

1011 1000

0000 0000

0000 0000

Change OTP Write Password

OTP Write

1100 0000

0000 0000

0000 0000

Change Reset Password

Reset

1100 1000

High Address

Low address

No-Password Memory Array Read

None

1101 1000

High Address

Low address

No-Password Memory Array Write

None

1110 1000

not used

not used

Reset Device Command (Resets Tamper bit)

Reset

1111 0000

not used

not used

ACK Polling command (Ends Password operation)

None

All the rest

Reserved