topic Re: Reset Vector for MCF5445x in ColdFire/68K Microcontrollers and Processors

Reset Vector for MCF5445x

Thad — Wed, 11 Feb 2009 05:25:16 GMT

I am writing a boot loader for an MCF5445x based target. I am wondering if it is possible to issue a soft reset but then have the reset vector route execution to the kernel I have just loaded into RAM (i.e. base address at 0x4002000) rather than do its usual load from ROM (0x00000000) or via SPI. I've been reading the MCF54455RM spec doc and my first impression is that it is not easily done, but perhaps I missed something.

Re: Reset Vector for MCF5445x

kmahan — Wed, 11 Feb 2009 05:34:13 GMT

I don't think you can. You either boot off a flexbus device or using the Serial Boot Flash (SBF) over SPI.

The two signals that control booting are BOOTMOD[1:0] (section 10.2.1 in the RM). Your options are:

Boot from Flexbus with defaults
Boot from Flexbus and override defaults via data bus
Boot from Flexbus and override defaults via the serial boot facility
Reserved (just for those wondering about the last bit combination)

You can't go directly to SDRAM. Also you'd need to setup the SDRAM controller before you could execute code from it.

--Kurt

Re: Reset Vector for MCF5445x

Thad — Wed, 11 Feb 2009 07:22:31 GMT

I thought as much. I was hoping for a shortcut, but it looks like I'll just have to set the board state manually before jumping to the kernel entry point. Thanks.