NXP Semiconductors MPC5644A, Reference Manual, Page: 276 / 1735

External Bus Interface (EBI)
MPC5644A Microcontroller Reference Manual, Rev. 6
276 Freescale Semiconductor
support a variety of external memory types, including Single Data Rate (SDR) burst mode flash, SRAM,
and asynchronous memories.
14.2.1 Overview
On the MPC5644A microcontroller, the EBI supports two sets of external signals: the EBI bus signals and
the calibration bus signals. They are very similar in function but have different purposes.
The calibration bus is a powerful development feature that enables system designers to interface dual-port
SRAM with a system under development. This gives the system the capability of loading engine
calibration data into SRAM instead of flash memory, making reprogramming the calibration data
considerably faster and avoids the necessity of having to reconfigure pins each time calibration data is
changed.
NOTE
The calibration signals are only available on the calibration package. It is a
very useful development feature but not used in production systems.
Figure 14-1 shows an overview of the EBI, including the calibration signals. Each external memory
component used is mapped to its own addressing region. Each region is separately programmable with
region address and bus configuration information.
Available bus configurations include 16-bit, 16-bit multiplexed and 32-bit multiplexed. In the multiplexed
modes. address and data signals are multiplexed on the same pins.