How do I read the USERCODE instruction out of Altera devices that support it without using a JAM File or JAM Byte-Code File?

Description

The USERCODE instruction can be read out of devices simply by loading the JTAG instruction register with the USERCODE instruction and shifting out the 32-bit code.

Reading the USERCODE instruction out of a device is a relatively simple JTAG process. Below is psuedocode that summarizes the process:

1. Traverse the JTAG state machine to the Shift-IR state
2. Load the USERCODE instruction
3. Traverse the JTAG state machine to the Shift-DR state
4. Shift out the 32-bit USERCODE value

The easiest way is to obtain the USERCODE is to use Jam™ Files or Jam Byte-Code Files, especially for embedded systems that already implement a Jam Player. The Jam language provides an easy interface to the JTAG port.

Refer to the device family data sheets for information on which devices support the USERCODE instruction.

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