Timestamp bitstreams with USR_ACCESS

Automatically inserting a timestamp into a bitstream is really easy with the USR_ACCESS primitive. All you need to do is include the following constraint in one of the XDC files that you are using:

Vivado will then automatically create a bitstream with the USR_ACCESS set to an 8 character hexadecimal code that represents the time that the .bit file was created. The time value is taken directly from the system of the computer on which the write_bitstream command is run.

The 32 bits of the timestamp are set out in the following format:

dddddd.MMMM.yyyyyy.hhhhh.mmmmmm.ssssss

• ddddd 5 bits for 31 days in a month
• MMMM 4 bits for 12 months in a year
• yyyyyy 6 bits for the last two digits of the year, 2000 to 2063
• hhhhh 5 bits for the hour in 24-hour format
• mmmmmm 6 bits for the minutes
• mmmmmm 6 bits for the seconds

You can check that the timestamp has been placed in the bitstream by consulting the Vivado implementation log, you should see a line like this:

Once the FPGA has been programmed, you can see the timestamp by looking at the programmed device properties in Vivado Hardware Manager..

Figure 1: Timestamp displayed in Hardware Manager