Data Sheet

SD2405ALPI IIC 串行接口的实时时钟IC
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The state of the data line represents valid data when, after a START condition, the data
line is stable for the duration of the HIGH period of the clock signal. The data on the line
must be changed during the LOW period of the clock signal. There is one clock pulse per bit
of data.
Each data transfer is initiated with a START condition and terminated with a STOP
condition. The number of data bytes transferred between START and STOP conditions is
not limited, and is determined by the master device. The information is transferred
byte-wise and each receiver acknowledges with a ninth bit.
(4) Acknowledge:
An acknowledge (ACK) is a software convention used to indicate a successful data transfer.
The transmitting device, either master or slave, releases the SDA bus after transmitting eight bits.
During the ninth clock cycle, the receiver pulls the SDA line LOW to acknowledge the reception
of the eight bits of data.
The SD2405AL responds with an ACK after recognition of a START condition followed by a
valid Identification Byte, and once again after successful receipt of an Address Byte. The
SD2405AL also responds with an ACK after receiving a Data Byte of a write operation. The
master must respond with an ACK after receiving a Data Byte of a read operation.
VALID DATA CHANGES, AND ACKNOWLEDGE RESPONSE FROM RECEIVER
6.2 The transmission format of data/command
(1)Device address
The high effective 7 bits (bit7---bit1) in the address byte are defined as device type ID. In
SD2405AL, these 7 bits are 0110010. The lowest bit0 is defined as R/W mode. When this bit is
“1”, it is read mode, while “0” is write mode.
The slave address:
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
0
1
1
0
0
1
0
R/W
BIT7—BIT1：The slave address of the SD2405AL is defined as 0110010
BIT0： R/W definition
“1” is read mode. “0” is
write mode.
(2) Data transmission format
At the end of data transmission/receiving stop condition is generated to complete
transmission. However, if start condition is generated without generating stop condition,
repeated start condition is met and transmission/receiving data may be continued by setting
the slave address again. Use this procedures when the transmission direction needs t be
changed during one transmission.