AR# 62020

Description

On the VCU108 evaluation kit, due to the revision implementation, a configuration failure (DONE will not go high) will be seen if the default bitstream options are used.

To prevent a master BPI configuration failure in Asynchronous read, the VU095 FPGA bitstream image MUST be compressed.

See the Solution section for the proper compression constraint syntax to use.

Details:

The VCU108 Evaluation Kit address pin connections between the Virtex UltraScale FPGA (VU095) and the Micron (PC28F00AG18FE) Flash are as follows:

• FPGA RS[0:1] pins are used in place of the FPGAs upper two address pins A[24:25]
  Note: FPGA LSB is A00 so the MSB is A25
• FPGA RS[0:1] connected to Micron flash A[25:26]
  Note: Flash LSB is A1 so the MSB is A26

The RS[0:1] pins effectively divide the flash into 4 sections based on the upper flash address pin setting (RS=00, RS=01, RS=10, and RS=11) allowing for easy revision selection with a dip switch.

The VCU108 RS[0:1] are pulled up or pulled down dependent on the on-board dip switch setting.

Once the RS pin selection is set, the configuration is started from one of the four image locations targeted by the switch setting.

Because the flash is effectively split into 4 sections by the RS pin implementation, the bitstream must be smaller than a quarter of the flash density.

The VCU108 Evaluation Kit has a 1Gb Micron flash and the VU095 FPGA bitstream slightly passes the quarter flash boundary (268,435,456 bits) by <7%.

When a bitstream running with the Master BPI Configuration Asynchronous read mode is greater than the next quarter flash boundary, it will wrap due to the RS static settings and not see the end of the bitstream.

Compression MUST be used when using the Master BPI Configuration Asynchronous read or a configuration failure will be seen.

Solution

Add the following constraint for compression to designs targeted for the VCU108 customer evaluation kit.

set_property  BITSTREAM.GENERAL.COMPRESS True [current_design]

If 4 images are not required to be programmed, then the Master BPI Configuration Synchronous read mode is another option. 

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