ISL12024 Intersil Corporation, ISL12024 Datasheet - Page 15

• Manufacturer Part Number: ISL12024
• Description: Real-Time Clock/Calendar
• Manufacturer: Intersil Corporation

Start Condition
All commands are preceded by the start condition, which is a
HIGH to LOW transition of SDA when SCL is HIGH. The
device continuously monitors the SDA and SCL lines for the
start condition and will not respond to any command until
this condition has been met (see Figure 13).
Stop Condition
All communications must be terminated by a stop condition,
which is a LOW to HIGH transition of SDA when SCL is
HIGH. The stop condition is also used to place the device
into the Standby Power Mode after a read sequence. A stop
condition can only be issued after the transmitting device
has released the bus (see Figure 13).
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
FROM TRANSMITTER
DATA OUTPUT
FROM RECEIVER
DATA OUTPUT
SCL FROM
MASTER
SDA
SCL
SDA
SCL
15
FIGURE 14. ACKNOWLEDGE RESPONSE FROM RECEIVER
FIGURE 12. VALID DATA CHANGES ON THE SDA BUS
FIGURE 13. VALID START AND STOP CONDITIONS
START
DATA STABLE
START
1
ISL12024
DATA CHANGE
SDA line LOW to acknowledge that it received the eight bits of
data (see Figure 14).
The device will respond with an acknowledge after
recognition of a start condition and if the correct Device
Identifier and Select bits are contained in the Slave Address
Byte. If a write operation is selected, the device will respond
with an acknowledge after the receipt of each subsequent
eight bit word. The device will not acknowledge if the slave
address byte is incorrect.
In the read mode, the device will transmit eight bits of data,
release the SDA line, then monitor the line for an
acknowledge. If an acknowledge is detected and no stop
condition is generated by the master, the device will continue
to transmit data. The device will terminate further data
transmissions if an acknowledge is not detected. The master
must then issue a stop condition to return the device to
Standby Power Mode and place the device into a known
state.
DATA STABLE
STOP
8
ACKNOWLEDGE
9
October 18, 2006
FN6370.1