Visible to Intel only — GUID: bhc1411109467475
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Introduction
System-Level Debugging Infrastructure
Virtual JTAG Interface Description
Run-Time Communication
Instantiating the Virtual JTAG Intel® FPGA IP Core
Simulation Support
Compiling the Design
SLD_NODE Discovery and Enumeration
Capturing the Virtual IR Instruction Register
AHDL Function Prototype
VHDL Component Declaration
VHDL LIBRARY-USE Declaration
Design Example: TAP Controller State Machine
Design Example: Modifying the DCFIFO Contents at Runtime
Design Example: Offloading Hardwired Revision Information
Document Revision History for the Virtual JTAG Intel® FPGA IP Core User Guide
Visible to Intel only — GUID: bhc1411109467475
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Read Logic
Two runtime instructions read the contents out of the FIFO. The IR decode logic selects the Push_out virtual DR chain and generates a single read pulse to the read logic when the POP instruction is active. The Push_out DR chain is parallel loaded upon the assertion of virtual_state_cdr and shifted out to TDO upon the assertion of virtual_state_sdr.
When the FLUSH instruction is shifted into the Virtual JTAG instance, the IR decode logic asserts the read_req line until the FIFO is empty. The bypass register is selected when the FLUSH instruction is active to maintain TDI‑to‑TDO connectivity. The figure below shows the read side logic for the DCFIFO.
Figure 21. Read Side Logic for DCFIFO Design Example