Jeffrey Collette

A question about using non-multiplexed mode for the Flexbus

Discussion created by Jeffrey Collette on Jun 20, 2007
Latest reply on Mar 13, 2009 by Manjula devi
I have a question about any limitations there might be in using non-multiplexed mode versus multiplexed mode for the Coldfire Flexbus.
We are in the design phase of a new circuit board that uses an MCF5485 CPU. We won't be using the PCI bus so would like to use non-multiplexed mode to eliminate the need for an address latch. The issue is, there are sections of the MCF5485 reference manual (Rev. 4) that seem to suggest that non-multiplexed mode is more limited in terms of the number of address and data lines that can be used at any one time. For instance, in the section on Bus Cycle Multiplexing in chapter 17, all of the figures that illustrate basic read and write cycles always show a net total of 32 address and data lines when non-multiplexed mode is used, ie, 16 Address with 16 data lines, or 24 address and 8 data lines. There is also a line in the description of Figure 17-16 that says "Notice that when the device port size is 32 bits, the only mode the bus supports is multiplexing address and data lines."
Am I misunderstanding something, or is the Flexbus really more limited in non-multplexed mode?

Message Edited by JeffC on 2007-06-20 06:16 PM