I2C Controller Reference Design

from Altera Corporation

Overview

The I2C Controller was designed for the MC68307 uC, provides a simplified interface to industry-standard I2C protocol. The I2CController is available in VHDL and is optimized for the Altera^®APEX™, Stratix^®, and Cyclone™ device families.

All of the register addresses are defined as constants in the VHDL source files and can be easily customized for customer use. The MBASE address is defined as a generic and can also be easily changed and customized for customer use. In addition, this design outputs the MCF signal on a pin which can be used by the uC as a quick indication that the I2C transfer is complete.

This design uses the I2C SCL signal as a clock. This requires that the SCL signal have clean, fast edges on both the rising and falling edges of this signal. Slow rise and fall times on this signal can show noise effects which can cause improper clocking of registers within the Stratix FPGA. If the loading of the SCL signal in the system is such that the rise and fall times are slow (>20nS), external buffers such as Schmitt Triggers will be required to interface to the FPGA.

Please also note that this design has been verified through simulations, but not on actual hardware.

Performance

Table 1 shows the performance results for the I2CController, which were generated with Quartus^®II software v4.2.

Demonstrated Altera Technology

• Apex II devices
• Apex 20K devices
• Stratix devices
• Cyclone devices

Block Diagram

Figure 1. System-Level Diagram of the I2C Controller

Reference Designs Disclaimer

These reference design illustrations may be used within Altera Corporation devices only and remain the copyrighted property of Altera. They are being provided on an "as-is" basis and as an accommodation, and therefore all warranties, representations, or guarantees of any kind (whether express, implied or statutory) including, without limitation, warranties of merchantability, non-infringement, or fitness for a particular purpose, are specifically disclaimed. Altera expressly does not recommend, suggest, or require that these examples be used in combination with any other product not provided by Altera.