Apple Battery Charger User Manual download pdf (Page 17)

17Maxim Integrated

USB Battery Charger Detectors

MAX14578E/MAX14578AE

C Serial Interface (MAX14578E)

Serial Addressing

The MAX14578E operates as a slave device that sends

and receives data through an I

C-compatible 2-wire

interface. The interface uses a serial-data line (SDA) and

a serial-clock line (SCL) to achieve bidirectional commu-

nication between master(s) and slave(s). A master (typi-

cally a microcontroller) initiates all data transfers to and

from the MAX14578E and generates the SCL clock that

synchronizes the data transfer. The SDA line operates as

both an input and an open-drain output. A pullup resis-

tor is required on SDA. The SCL line operates only as an

input. A pullup resistor is required on SCL if there are

multiple masters on the 2-wire interface, or if the master

in a single-master system has an open-drain SCL output.

Each transmission consists of a START condition (Figure

4) sent by a master, followed by the MAX14578E 7-bit

slave address plus a R/W bit, a register address byte,

one or more data bytes, and finally a STOP condition.

START and STOP Conditions

Both SCL and SDA remain high when the interface is not

busy. A master signals the beginning of a transmission

with a START (S) condition by transitioning SDA from

high to low while SCL is high (see Figure 5). When the

master has finished communicating with the slave, it

issues a STOP (P) condition by transitioning SDA from

low to high while SCL is high. The bus is then free for

another transmission.

Figure 4. I

C Interface Timing Details

Figure 5. START and STOP Conditions

SDA

SCL

HD:STA

LOW

HIGH

SU:DAT

SU:STA

SU:STO

BUF

HD:STA

HD:DAT

START

CONDITION

STOP

CONDITION

START

CONDITION

REPEATED

START CONDITION

SDA

SCL

START

CONDITION

STOP

CONDITION

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 23

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Apple Battery Charger User Manual Page 17

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