MarsBoard/JTAG

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Connection

The marsboard P2 connector includes the UART 0 and JTAG signals as 3.3V TTL!.

You will need to make a JTAG adapter to suit your JTAG debugger.

ARM 20-pin JTAG MarsBoard P2 Header
pin 1 - Vref pin 63 - VCC-3V3
pin 5 - TDI pin 70 - JTAG-DI
pin 7 - TMS pin 67 - JTAG-MS
pin 9 - TCK pin 68 - JTAG-CK
pin 13 - TDO pin 68 - JTAG-DO
pins 2-20 (even) pin 64 - GND

Check your JTAG tool's cable details for alternate pinouts.

Notes:

On Allwinner A20:

  • Ensure Linux power-management is disabled and both CPUs are enabled to connect reliably, or setup your debugger to use a single-core only.
 echo userspace > /sys/bus/cpu/devices/cpu0/cpufreq/scaling_governor
 echo 1 > /sys/bus/cpu/devices/cpu0/online
 echo 1 > /sys/bus/cpu/devices/cpu1/online

Lauterbach Trace32

The following are a single-core and dual-core version of the script.

   ; MarsBoard A20 uniprocessor Trace32 Script
   ; connect to CPU0 only
   ; 2013-08-12

   RESet
   SYStem.CPU CortexA7MPCore
   SYStem.CONFIG CoreNumber 1.
   CORE.ASSIGN 1.

   SYStem.JTAGCLOCK 20MHz

   SYStem.CONFIG MEMORYACCESSPORT 0.
   SYStem.CONFIG DEBUGACCESSPORT 1.
   SYStem.CONFIG COREBASE              0x80110000
   SYStem.CONFIG BMCBASE               0x80111000

   SYStem.Option EnReset OFF

   ; Allwinner A20 Details
   MAP.BONCHIP 0xffff0000--0xffff7fff

   Break.Implementation Program Onchip

   SYStem.Up

The script below connects to the A20 configured in SMP mode with both CPUs powered on. If you are in the bootloader or trying to connect while only CPU0 is online, use the uni-processor script.

   ; MarsBoard A20 Dual-Core Trace32 Script
   ; This script requires BOTH cores to be powered on!
   ; 2013-08-12

   RESet
   SYStem.CPU CortexA7MPCore
   SYStem.CONFIG CoreNumber 2.
   CORE.ASSIGN 1. 2.

   SYStem.JTAGCLOCK 20MHz

   SYStem.CONFIG MEMORYACCESSPORT 0.
   SYStem.CONFIG DEBUGACCESSPORT 1.
   SYStem.CONFIG COREBASE              0x80110000 0x80112000
   SYStem.CONFIG BMCBASE               0x80111000 0x80113000

   SYStem.Option EnReset OFF

   ; Allwinner A20 Details
   MAP.BONCHIP 0xffff0000--0xffff7fff

   Break.Implementation Program Onchip

   SYStem.Up

See Also

JTAG

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