isl12022m Intersil Corporation, isl12022m Datasheet - Page 23

• Manufacturer Part Number: isl12022m
• Description: Real Time Clock With Embedded Crystal, ??5ppm Accuracy
• Manufacturer: Intersil Corporation

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 (see Figure 16).
The ISL12022M 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
ISL12022M 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.
SDA OUTPUT FROM
SDA OUTPUT FROM
TRANSMITTER
SCL FROM
RECEIVER
SDA
SCL
MASTER
SIGNALS FROM
SIGNAL AT SDA
SIGNALS FROM
THE ISL12022M
THE MASTER
FIGURE 17. BYTE WRITE SEQUENCE (SLAVE ADDRESS FOR CSR SHOWN)
23
START
FIGURE 15. VALID DATA CHANGES, START AND STOP CONDITIONS
START
FIGURE 16. ACKNOWLEDGE RESPONSE FROM RECEIVER
HIGH IMPEDANCE
S
T
A
R
T
1
IDENTIFICATION
1
1
0
BYTE
1
STABLE
1 1 1
DATA
ISL12022M
0
WRITE
A
C
K
CHANGE
DATA
0 0 0 0
ADDRESS
Device Addressing
Following a start condition, the master must output a Slave
Address Byte. The 7 MSBs are the device identifiers. These
bits are “1101111” for the RTC registers and “1010111” for the
User SRAM.
The last bit of the Slave Address Byte defines a read or write
operation to be performed. When this R/W bit is a “1”, a read
operation is selected. A “0” selects a write operation (refer to
Figure 18).
After loading the entire Slave Address Byte from the SDA bus,
the ISL12022M compares the device identifier and device
BYTE
STABLE
DATA
A
C
K
8
DATA
BYTE
HIGH IMPEDANCE
STOP
ACK
9
A
C
K
S
T
O
P
December 18, 2008
FN6668.4