MC9S12NE64 with large (4MB) RAM buffer

[okalex]

Hello all,

I'm trying to decide on a microprocessor for a new design, and NE64 is very close to fulfilling all of our requirements, but not quite. The design requires Ethernet (I suppose on-chip Ethernet is not absolutely required, as we can add an external controller, but it would be very nice), I2C, and a 4MB external memory buffer. Looking at the datasheet for the NE64, it seems that the maximum size of memory that can be accessed is 1MB, if paging is used. Does anyone have experience adding more memory by using GPIO for additional address lines? Is this even possible?

Sincerely,
Alex Parkinson

[Goz]

Yup it is totally paossible I have used external memory with the NE64 in a product I designed, it is a pain in the backside as the memory lines are multiplexed, which means you need to use a de-multiplexer and a sample and hold device (D-type flip-flop based). Be aware, if you use external memory then you can ONLY use the ethernet interface at 10BaseT.

[Nouchi]

Hi,

The MCF5223x family is the NE64 equivalent in the coldfire world, but the mcf5207 or mcf5208 will be better for your design , because it has a built-in SD/DDR RAM controller (up to 512Mbytes) and an integrated FEC you just have to add PHY device.
see:
http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MCF5207



Emmanuel

[rocco]

Hi, Alex:

I can't say whether or not it is possible, but I can tell you that bit would be painful. Memory addressing is not a strong point for the S12s.

I would suggest looking at one of the Ethernet-enabled ColdFire processors, as they can access that much memory natively.