AT88SC0204CA-WI Просмотр технического описания (PDF) - Atmel Corporation

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AT88SC0204CA-WI

Atmel CryptoMemory

Atmel Corporation 

8.1 Security Fuses

There are three fuses on the device that must be blown during the device personalization process. Each fuse locks certain

portions of the configuration zone as OTP (One-Time Programmable) memory. Fuses are designed for the module

manufacturer, card manufacturer and card issuer and should be blown in sequence, although all programming of the device

and blowing of the fuses may be performed at one final step.

9. Communication Security Modes

Communications between the device and host operate in three basic modes. Standard mode is the default mode for the

device after power-up. Authentication mode is activated by a successful authentication sequence. Encryption mode is

activated by a successful encryption activation following a successful authentication.

Table 9-1. Communication Security Modes(1)

Mode

Standard

Authentication

Encryption

Configuration Data

Clear

Clear

Clear

User Data

Clear

Clear

Encrypted

Passwords

Clear

Encrypted

Encrypted

Data Integrity Check

MDC(1)

MAC(1)

MAC(1)

Note:

1. Configuration data include viewable areas of the configuration zone except the passwords:

 MDC: Modification Detection Code

 MAC: Message Authentication Code

10. Security Options

10.1

Anti-tearing

In the event of a power loss during a write cycle, the integrity of the device’s stored data is recoverable. This function is

optional: the host may choose to activate the anti-tearing function, depending on application requirements. When anti-tearing

is active, write commands take longer to execute, since more write cycles are required to complete them, and data is limited to

a maximum of eight bytes for each write request.

Data is written first into a buffer zone in EEPROM instead of the intended destination address, but with the same access

conditions. The data is then written in the required location. If this second write cycle is interrupted due to a power loss, the

device will automatically recover the data from the system buffer zone at the next power-up. Non-volatile buffering of the data

is done automatically by the device.

During power-up in applications using anti-tearing, the host is required to perform ACK polling in the event that the device

needs to carry out the data recovery process.

10.2

Write Lock

If a user zone is configured in the write lock mode, the lowest address byte of an 8-byte page constitutes a write access byte

for the bytes of that page.

Example: The write lock byte at $080 controls the bytes from $081 to $087

Table 10-1. Write Lock Example

Address

$080

$0

11011001

$1

xxxx xxxx

locked

$2

xxxx xxxx

locked

$3

xxxx xxxx

$4

xxxx xxxx

$5

xxxx xxxx

locked

$6

xxxx xxxx

$7

xxxx xxxx

Atmel AT88SC0204CA [Summary DATASHEET] 11

5202FS−CRYPTO−12/11

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