MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 861
Chapter 22External Bus Interface (S12XEBIV2)

22.1 Introduction

This document describes the functionality of the MC9S12XDP512 block controlling the external bus
interface.
The MC9S12XDP512 controls the functionality of a non-multiplexed external bus (a.k.a. ‘expansion bus’)
in relationship with the chip operation modes. Dependent on the mode, the external bus can be used for
data exchange with external memory, peripherals or PRU, and provide visibility to the internal bus
externally in combination with an emulator.

22.1.1 Features

The MC9S12XDP512 includes the following features:
Output of up to 23-bit address bus and control signals to be used with a non-muxed external bus
Bidirectional 16-bit external data bus with option to disable upper half
Visibility of internal bus activity

22.1.2 Modes of Operation

Single-chip modes
The external bus interface is not available in these modes.
Expanded modes
Address, data, and control signals are activated on the external bus in normal expanded mode and
special test mode.
Emulation modes
The external bus is activated to interface to an external tool for emulation of normal expanded mode
or normal single-chip mode applications.
Refer to the S12X_MMC section for a detailed description of the MCU operating modes.