external SRAM interface with MPC555

Hello,

 SRAM is required to be used with an MPC555, in an Avionics 
application (-55C to 125C ambient temperature).

Program code will be downloaded from Flash memory(internal flash of 
MPC555) to the SRAM. SRAM must be fast enough for the MPC555 to run 
code at the full 40MHz speed?

 The minimum total amount of SRAM that is required is 256Kbytes, up 
to 2Mbytes if possible. it can be x32 configuration or x16 
configuration, 

The usage of internal flash of the microcontroller and  external 
SRAM interfaced to microcontroller MPC555 can be done?

Is it possible to interface SDRAM to MPC555.If yes how the control 
signals will be interfaced?

Thanks,
Sushmitha