topic MCF5445x crossbar switch (core to external memory) compared to MCF547x/8x XL bus in ColdFire/68K Microcontrollers and Processors

MCF5445x crossbar switch (core to external memory) compared to MCF547x/8x XL bus

M_H_ — Wed, 02 Jan 2008 20:32:56 GMT

I am currently using the MCF5474 but need to change to a processor with a working USB. The MCF5474 also has a speed problem with accessing external memory and while changing processor I would like to see that improved.

Has the access time to SDRAM and external SRAM been improved on the MCF5445x family over that seen on the MCF547x and MCF548x ?

By that I mean does the crossbar switch (XBS) on the MCF5445x work faster than the XL bus on the MCF547x/8x ? If so, are there any figures to compare the relative speeds?

Re: MCF5445x crossbar switch (core to external memory) compared to MCF547x/8x XL bus

wuwenbin — Sat, 02 Feb 2008 09:53:50 GMT

I want to know your 5474 SDRAM(DDR?) SPEED. Our test result show 5372 (80MHz) and 5474(133MHz) DDR SDRAM SPEED nearly equal. So we can think XBS is much faster than XLB.

Re: MCF5445x crossbar switch (core to external memory) compared to MCF547x/8x XL bus

M_H_ — Fri, 15 Feb 2008 20:02:08 GMT

Thanks for your answer. I don't actually have any SDRAM on my board. I was just assuming that if the SDRAM speed was better on the XBS then the SRAM speed would also be better. Your comment gives me hope.

I'm just about to start testing my new processor board where I have replaced the MCF5474 with the MCF54450 so whatever the speed is I'm going to have to live with it now anyway.

The USB on the MCF54450 seems to be improved compared with the MCF5474 (I haven't measured speed yet). I have that working on the evalution board. The documentation could be improved though. It doesn't help when the documentation and the example program don't agree.