MC9S12XD256MAL Datasheet, PDF (785/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 21
External Bus Interface (S12XEBIV2)
21.1 Introduction
This document describes the functionality of the XEBI block controlling the external bus interface.
The XEBI 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.
21.1.1 Features
The XEBI 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
21.1.2 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.
MC9S12XDP512 Data Sheet, Rev. 2.21
Freescale Semiconductor
787