Rainbow Electronics MAX5970 User Manual

Page 39

0V to 16V, Dual Hot-Swap Controller with 10-Bit

Current and Voltage Monitor and 4 LED Drivers

MAX5970

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Figure 8. Acknowledge

Early STOP Conditions

The MAX5970 recognizes a STOP condition at any point
during transmission except if a STOP condition occurs in
the same high pulse as a START condition. This condi-
tion is not a legal I

C format. At least one clock pulse

must separate any START and STOP condition.

REPEATED START Conditions

A REPEATED START (Sr) condition may indicate a
change of data direction on the bus. Such a change
occurs when a command word is required to initiate
a read operation (see Figure 4). Sr may also be used
when the bus master is writing to several I

C devices

and does not want to relinquish control of the bus. The
MAX5970 serial interface supports continuous write
operations with or without an Sr condition separating
them. Continuous read operations require Sr conditions
because of the change in direction of data flow.

Acknowledge

The acknowledge bit (ACK) is the 9th bit attached to any
8-bit data word. The receiving device always generates
an ACK. The MAX5970 generates an ACK when receiv-
ing an address or data by pulling SDA low during the
9th clock period (see Figure 8). When transmitting data,
such as when the master device reads data back from
the MAX5970, the MAX5970 waits for the master device
to generate an ACK. Monitoring ACK allows for detec-
tion of unsuccessful data transfers. An unsuccessful
data transfer occurs if the receiving device is busy or if
a system fault has occurred. In the event of an unsuc-
cessful data transfer, the bus master should reattempt
communication at a later time. The MAX5970 generates
a NACK after the slave address during a software reboot
or when receiving an illegal memory address.

SCL

SDA BY

TRANSMITTER

SDA BY

RECEIVER

START

CONDITION

CLOCK PULSE FOR ACKNOWLEDGE