External Bus Interface (EBI)MPC5644A Microcontroller Reference Manual, Rev. 6276 Freescale Semiconductorsupport a variety of external memory types, including Single Data Rate (SDR) burst mode flash, SRAM,and asynchronous memories.14.2.1 OverviewOn the MPC5644A microcontroller, the EBI supports two sets of external signals: the EBI bus signals andthe 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-portSRAM with a system under development. This gives the system the capability of loading enginecalibration data into SRAM instead of flash memory, making reprogramming the calibration dataconsiderably faster and avoids the necessity of having to reconfigure pins each time calibration data ischanged.NOTEThe calibration signals are only available on the calibration package. It is avery useful development feature but not used in production systems.Figure 14-1 shows an overview of the EBI, including the calibration signals. Each external memorycomponent used is mapped to its own addressing region. Each region is separately programmable withregion address and bus configuration information.Available bus configurations include 16-bit, 16-bit multiplexed and 32-bit multiplexed. In the multiplexedmodes. address and data signals are multiplexed on the same pins.
