Virtual JTAG Intel® FPGA IP Core User Guide

ID 683705
Date 8/12/2021
Document Table of Contents

Virtual IR/DR Shift Transaction that Captures Current VIR/VDR Values

The Tcl command examples below show that the no_captured_value option is not set in the Virtual IR/DR shift commands and the underlying JTAG shift commands associated with each. In the VIR shift command, the command returns two device_dr_shift commands.
Virtual IR Shift

device_virtual_ir_shift -instance_index 0 -ir_value 1 \

-no_captured_ir_value -show_equivalent_device_ir_dr_shift


Info: Equivalent device ir and dr shift commands

Info: device_ir_shift -ir_value 14

Info: device_dr_shift –length 5 –dr_value 0B –value_in_hex

Info: device_dr_shift -length 5 -dr_value 11 -value_in_hex

Virtual DR Shift

device_virtual_dr_shift -instance_index 0 -length 8 -dr_value \

04 -value_in_hex -show_equivalent_device_ir_dr_shift


Info: Equivalent device ir and dr shift commands

Info: device_ir_shift -ir_value 12

Info: device_dr_shift -length 8 -dr_value 04 -value_in_hex

The figure below shows an example of VIR/VDR Shift Commands with captured IR values. DR Scan Shift 1 is the VIR_CAPTURE command, as shown in the figure below. It targets the VIR of the sld_hub. This command is an address cycle to select the active VIR chain to shift after jtag_state_cir is asserted. The HUB_FORCE_IR capture must be issued whenever you capture the VIR from a target SLD node that is different than the current active node. DR Scan Shift 1 targets the SLD hub VIR to force a captured value from Virtual JTAG instance 1 and is shown as the VIR_CAPTURE command. DR Scan Shift 2 targets the VIR of Virtual JTAG instance.

Figure 12. Equivalent Bit Pattern Shifted into Device by VIR/VDR Shift Commands with Captured IR Values
Note: If you use an embedded processor as a controller for the JTAG chain and your Virtual JTAG Intel® FPGA IP core instances, consider using the JAM Standard Test and Programming Language (STAPL). JAM STAPL is an industry‑standard flow‑control‑based language that supports JTAG communication transactions. JAM STAPL is open source, with software downloads and source code available from the Intel® website.

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