Add Jtag Port

From NAS-Central Buffalo - The Linkstation Wiki

Revision as of 00:12, 13 July 2007

Cable required

This document is a work in progress. It explains how to fit the internal on-chip debug (OCD) port on a Linkstation, Kuro-Box or Kuro-Box/HG to a PC interface.

Adding the JTAG Port

Locate the pads

The pads are labelled CN5 and can be seen just above the serial level converter (where the yellow, orange, and red wires start to split) in this photo

Connector Pin-outs

In order to use this port, you should bridge R67.

Baulab posted cable schematics, some pictures of the assembled jtag cable, and software needed.

According to http://www.abatron.ch/Files/ManAccessCOP-2000C.pdf and http://www.freescale.com/files/soft_dev_tools/doc/user_guide/CWH-UTP-UG.pdf the following pins are used for a PPC COP/JTAG interface:

Pin Name       Description
 1  TDO        JTAG Test Data Out
 2  QACK       Not Needed
 3  TDI        JTAG Test Data In
 4  TRST       JTAG Test Reset
 5  HALTED     Not Needed 
 6  Vcc Target 1.8 – 5.0V:
               This is the target reference voltage. It indicates that the target has power and it is also used
               to create the logic-level reference for the input comparators. It also controls the output logic
               levels to the target. It is normally fed from Vdd I/O on the target board.
               3.0 – 5.0V:
               This input is used to detect if the target is powered up. If there is a current
               limiting resistor between this pin and the target Vdd, it should be 100 Ohm or less.
 7  TCK        JTAG Test Clock
 8  CKSI       Not Connected ??
 9  TMS        JTAG Test Mode Select
10  <reseved>
11  SRESET     Soft-Reset
12  GROUND     System Ground
13  HRESET     Hard-Reset
14  <reseved>
15  CKSO       Not Connected on the 8421
16  GROUND     System Ground

On-Chip Debug (OCD) connector

The internal OCD port uses an electrical standard known as JTAG/COP. The signals have to be buffered to protect the hardware from damage and we use a JTAG wiggler to do this.

Those with some electrical experience could build their own circuit, but most will opt for ordering one.

Schematics and Software to build your own

• Building a JTAG Interface
• http://hri.sourceforge.net/tools/

Buy one

• Commercial - The Macraigor Wiggler seems to be the cheapest at $150.
• Hobby - Could the 20-pin Olimex ARM-JTAG be modified to work with Kuro-Box? $20.
• A quick search on ebay will find many buffered JTAG cables for less than $20.