User's Manual

AC65/AC75 Hardware Interface Description

Confidential / Preliminary

AC65/AC75_hd_v00.372 Page 59 of 118 2006-08-03

3.13 I

C Interface

C is a serial, 8-bit oriented data transfer bus for bit rates up to 400kbps in Fast mode. It

consists of two lines, the serial data line I2CDAT and the serial clock line I2CCLK.

The AC65/AC75 module acts as a single master device, e.g. the clock I2CCLK is driven by

module. I2CDAT is a bi-directional line.

Each device connected to the bus is software addressable by a unique 7-bit address, and

simple master/slave relationships exist at all times. The module operates as master-

transmitter or as master-receiver. The customer application transmits or receives data only

on request of the module.

To configure and activate the I

C bus use the AT^SSPI command. If the I

C bus is active the

two lines I2CCLK and I2DAT are locked for use as SPI lines. Vice versa, the activation of the

SPI locks both lines for I

C. Detailed information on the AT^SSPI command as well

explanations on the protocol and syntax required for data transmission can be found in [1].

The I

C interface can be powered from an external supply or via the VEXT line of

AC65/AC75. If connected to the VEXT line the I

C interface will be properly shut down when

the module enters the Power-down mode. If you prefer to connect the I

C interface to an

external power supply, take care that VCC of the application is in the range of V

VEXT

and that

the interface is shut down when the PWR_IND signal goes high. See figures below as well

as Section 7 and Figure 46.

In the application I2CDAT and I2CCLK lines need to be connected to a positive supply

voltage via a pull-up resistor.

For electrical characteristics please refer to Table 26.

GSM module

I2CDAT

I2CCLK

GND

I2CDAT

I2CCLK

GND

Application

VCC

VEXT

Figure 19: I

C interface connected to VCC of application