Low-Level Debugging

This document outlines various helpful commands for debugging the firmware. These will mostly use the Xilinx System Debugger (xsdb). This is a command line tool which interacts with the hardware. One can program the FPGA, read memory and registers, etc.

See the official Xilinx documentation for more xsdb commands. Also, see this helpful guide for debugging Zynq-based projects.

Open xsdb prompt

  1. Run C:\Xilinx\Vivado\2017.2\bin\xsdb.bat

Connect to AMDC via xsdb

  1. Ensure AMDC JTAG is plugged into PC

  2. Ensure AMDC is powered on and in a reset state

  3. connect – should print tcfchan#0 if connected

  4. targets – should print list of targets, 1-4

Program AMDC through development environment

  1. Load the FPGA bitstream and DSP firmware

Read registers of running program

In xsdb:

  1. targets 2 – connect to the ARM Cortex-A9 core that the code is running on

  2. rrd – prints registers with current values

Read registers of hardware peripherials

In xsdb:

  1. targets 1 – connect to APU

  2. rrd – lists all possible peripherials to read from

  3. Example: rrd uart0 – read UART0 registers

Read memory address

Ensure code if up and running. In xsdb:

  1. targets 2 – connect to the running ARM Cortex-A9 core

  2. mrd <memory_address> – read from hex global memory address

Determine why reboot occurs:

Boot AMDC with your code prior to reboot. Make sure it is running fine.

In xsdb:

  1. targets 1 – connect to API

  2. rrd slcr – read from slcr h/w

  3. Look for reboot_status in left column. This encodes the reason for the last reboot (persisted through POR). Bits should be set to indicate JTAG debug reset…

  4. rwr slcr reboot_status 0x0 – clear the REBOOT_STATUS register

  5. Force the reboot to occur by breaking the firmware, etc

  6. rrd slcr – reread the REBOOT_STATUS register

  7. Lookup bits that have been set: https://www.xilinx.com/support/answers/52030.html