FT4222HQ-C-R datasheet(20/49 Pages) FTDI

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FT4222H USB2.0 TO QUADSPI/I2C BRIDGE IC

1.3

Document No.: FT_001011 Clearance No.: FTDI#405

5.3

I2C Bus Interface

C (Inter Integrated Circuit) is a multi-master serial bus invented by Philips. I

2C uses two bi-directional

open-drain wires called serial data (SDA) and serial clock (SCL). Common I²C bus speeds are standard

mode (SM) with bit rate up to 100 Kbit/s, fast mode (FM) with bit rate up to 400 Kbit/s, Fast mode plus

(FM+) with bit rate up to 1 Mbit/s, and High Speed mode (HS) with the bit rate up to 3.4 Mbit/s.

An I2C bus node can operate either as a master or a slave:



Master node

– issues the clock and addresses slaves



Slave node

– receives the clock line and address.

The FT4222H can operate as a master or slave, and is capable of being set to the speed modes defined in

the I2C bus specification. Besides the speed mode defined in the I2C standard specification, the I2C

controller of the FT4222H can support flexible SCL frequencies defined by the following function

�� =

��

��∗(��+��)

�� = �� ; �� = ��, ��, ��, … … , ��

When the target frequency is below 100 KHz, M will be equal to 8; otherwise, M will be equal to 6. For

example, to generate a 2.5MHz frequency on SCL, M will be selected as 6. Then with an operating clock

frequency equal to 60MHz the user can set N as 3. The SCL frequency for I2C master mode can be set via

the FT4222_I2CMaster_Init command defined in the support library, LibFT4222. Refer to the User Guide

For LibFT4222 for further details.

5.3.1 I2C Pin Definition

The I2C function in the FT4222H is a fully configurable I2C master/slave device. When the chip

configuration is set as CNFMODE0 or CNFMODE3 and the USB-to-I2C bridge function is enabled via the

FT4222_I2CMaster_Init API which is defined in the support library LibFT4222. The pins of the FT4222H

will be mapped accordingly. The I2C pins are



Clock – SCL (pin-13), as clock output with open-drain design when I2C bus is set as master.

as clock input when I2C bus is set as slave.



Data

– SDA (pin-14), command/address/data transfer between master and slave with open-

drain design

5.3.2 I2C Bus Protocol

There are four potential modes of operation for a given bus device, although most devices only use a

single role (Master or Slave) and its two modes (Transmit and Receive):



Master transmit – sending data to a slave



Master receive – receiving data from a slave



Slave transmit – sending data to a master



Slave receive

– receiving data from the master

The following figure shows the basic I2C bus protocol

Figure 5.6 I2C Bus Protocol

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