Simple Bootloader Debuging

From: Dale Ziebarth (dziebarth_at_hotmail.com)
Date: 06/29/04 

Date: Tue, 29 Jun 2004 16:11:33 -0500

I am writing a bootloader for a PXA255 (Cotulla) based board. I know that
the hardware works because I can download a Linux bootloader to it and
download an image fine.

I modified the Intel DBPXA255 BSP (XSC1BD/Lubbock) bootloader to remove the
Sabinal code and the FPGA related code (specifically in the FWXSC1.S file)
because I don't have those items. After modifying the BOOT.BIB, MEMMAP.INC
and related files I built the NB0 file and burned it into flash using a JTAG
wiggler and Jflash. Once I power it off and back on I don't know where it
gets hung up because it does not send a message out the debug serial port as
I expected. After much learning about how the memory map works and
verification that the NB0 file contained what I expected I decided to look
at the the low level code that executes before "main" is ever called.

At the begining of the Reset_Handler code (in FWXSC1.S) I added an
initialize of the FFUART (using the InitFFUART macro) and transmit of three
characters (0x30, 0x41 and 0x61) out the FFUART port. (After the early
refresh fix, pre-initialize code and initalization of GPIO and MEMC). Only
one character comes out the port and it is a 'FF'.

I'm baffled. Any ideas on what I am doing wrong? Is there some way using
the JTAG wiggler I have that I could single step through code? I don't need
anything fancy, just an idea of what is being executed.

Relevant Pages

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