39.1 Overview

The External Bus Interface (EBI), only available on 176 & 208 pin devices, is designed to provide data transfer between external devices and the embedded Memory Controller of an ARM-based microcontroller.

The EBI module generates the signals that control the access to the external memory devices or peripheral devices. It has 4 chip selects, a 24-bit address bus, and a configurable 8 or 16-bit data bus. Separate read and write control signals allow for direct memory and peripheral interfacing. Read and write signal waveforms are fully adjustable.

The EBI module can manage wait requests from external devices to extend access times. The EBI module provides an automatic Slow clock mode. In Slow clock mode, it switches from user-programmed waveforms to slow-rate specific waveforms on read and write signals. It also supports asynchronous burst read in Page mode access for page sizes up to 32 bytes.