AT88SC0404CA Просмотр технического описания (PDF) - Atmel Corporation

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AT88SC0404CA

CryptoMemory®

Atmel Corporation 

AT88SC0404CA

8. Device Operations for Synchronous Protocols

8.1 Clock and Data Transitions

The SDA pin is normally pulled high with an external device. Data on the SDA pin may change

only during SCL low time periods (see Figure 8-3 on page 8). Data changes during SCL high

periods will indicate a start or stop condition as defined below.

8.1.1

Start Condition

A high-to-low transition of SDA with SCL high defines a START condition which must precede all

commands (see Figure 8-4 on page 8).

8.1.2

Stop Condition

A low-to-high transition of SDA with SCL high defines a STOP condition. After a read sequence,

the STOP condition will place the EEPROM in a standby power mode (see Figure 8-4 on page

8).

8.1.3

ACKNOWLEDGE

All addresses and data words are serially transmitted to and from the EEPROM in 8-bit words.

The EEPROM sends a zero to acknowledge that it has received each word. This happens dur-

ing the ninth clock cycle (see Figure 8-5 on page 9).

8.2 Memory Reset

After an interruption in communication due protocol errors, power loss or any reason, perform

"Acknowledge Polling" to properly recover from the condition. Acknowledge polling consists of

sending a start condition followed by a valid CryptoMemory command byte and determining if

the device responded with an ACKNOWLEDGE.

Figure 8-1. Bus Time for 2-Wire Serial Communications. SCL: Serial Clock, SDA: Serial Data I/O

7

5203CS–CRYPT–5/09

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