MC9S12XDT256 EBI module

[sfb]

Hi,

We used MC9S12D64 MEBI feature for addressing 128K external RAM. Now we want to use MC9S12XDT256 instead of MC9S12D64. These processors are pin to pin compatible. But I saw that for 12XDT256 there is an EBI block. Can we use our external bus interface for XDT256 without changing anything.

Second question is, what is the code size for XGATE area?

Message Edited by sfb on 2007-11-09 12:21 PM

[Steve]

The EBI is a different design to the MEBI on the S12D so you will not be able to reuse your current design. The new approach should greatly simplify the circuitry required. The EBI is non-multiplexed and only available on the 144pin device so it will not be pin-pin compatible for you.

Also have a look at AN2708 which describes the external bus on the S12XD.

[sfb]

Thanks for your reply. Can you say anything about XGATE capacity?

[Steve]

I'm not sure what you mean by "capacity". If you are talking about performance then the gain compared to the S12D will vary from +50% to +400% at the same bus speed depending on the task at hand. There are loads of app notes describing how it works and performance numbers for certain tasks but it may be more accurate to run some of your existing code on XGATE and see how it goes. You'll need an S12X toolchain and either a simulator or hardware.

Since you're moving from S12D then AN2615 is a good place to start. Search for "XGATE" on our website and you'll see about 27 application note hits including a bunch of software. The "XGATE Library" app notes include performance numbers for several activities.