Cyclone® V Hard Processor System Technical Reference Manual

ID 683126
Date 8/28/2023
Public
Document Table of Contents

7.3.2. Communicating with the JTAG TAP Controller

After the system manager undergoes a cold reset, access to the JTAG TAP controller in the FPGA control block is through the dedicated FPGA JTAG I/O pins. If necessary, you can configure your system to use the scan manager to provide the HPS processor access to the JTAG TAP controller, instead. This feature allows the processor to send JTAG instructions to the FPGA portion of the device.

To connect scan chain 7 between the scan manager and the FPGA JTAG TAP controller, the following features must be enabled:

  • The scan chain for the FPGA JTAG TAP controller—To enable scan chain 7, set the fpgajtag field of the en register in the scan manager. For more information, refer to "Scan Manager Address Map and Register Definitions".
  • The FPGA JTAG logic source select—This source select determines whether the scan manager or the dedicated FPGA JTAG pins are connected to the FPGA JTAG TAP controller in the FPGA portion of the device. On system manager cold reset, the dedicated FPGA JTAG pins are selected. The source select is configured through the fpgajtagen bit of the ctrl register in the scanmgrgrp group of the system manager. The FPGA JTAG pins and scan manager connection to the TAP controller must both be inactive when switching between them. The mechanism to ensure both are inactive is user-defined.
Note: Before connecting or disconnecting the scan chain between the scan manager and the FPGA JTAG TAP controller, ensure that both the FPGA JTAG TCK and scan manager TCK signals are de-asserted. Altera recommends resetting the FPGA JTAG TAP controller using the scan manager's nTRST signal after the scan manager is connected to the controller.