Specifications

AC65/AC75 Hardware Interface Description

3.13 I

C Interface

AC65_AC75_HD_v01.002 Page 54 of 117 2006-10-30

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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 trans-

mission 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 VVEXT and that the interface is shut down when the PWR_IND signal goes high. See figures below as

well as Section 7 and Figure 47.

In the application I2CDAT and I2CCLK lines need to be connected to a positive supply voltage via a pull-up resis-

tor.

For electrical characteristics please refer to Table 26.

Figure 19: I

C interface connected to VCC of application

Figure 20: I

C interface connected to VEXT line of AC65/AC75

Note: Good care should be taken when creating the PCB layout of the host application: The traces of I2CCLK

and I2CDAT should be equal in length and as short as possible.