AR# 53615

Description

Some ZC702 Rev 1.0 boards could exhibit an issue related the Digilent USB-JTAG SMT1 modules which manifests itself in two ways:

1. DS2 INIT LED unexpectedly illuminates red, or
2. Zynq-7000 Z7020 device or ARM processor is un-detectable in the JTAG chain

Solution

A footprint incompatibility between the Digilent USB JTAG SMT1 and SMT2 modules can result in unexpected behavior on ZC702 boards with serial numbers beginning with 1224-xxxx.
This can result in failure to detect the ARM processor in the JTAG chain and may cause the INIT LED to illuminate red and remain red as the ARM processor is held in reset.

ZC702 Rev 1.0 boards whose serial number begin with S/N 1224-xxxx may be affected by this issue. 


Following is a simple board modification to prevent this issue from occurring.

1. Locate U23, Digilent SMT1 USB-JTAG module, on top side of board.  U23 is located near Mounting Hole MH6.
2. Next, you will cut a trace between the U23-11 PAD and neighboring Via (cut per Red line marking) with an X-ACTO blade or similar device, as shown below:

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