Altera Virtual JTAG IP Core - Manual (Page 3)

Typical Circumstances for Use Description Tool
You want to view and edit the
contents of either the instruction
cache or data cache of a Nios
® II
processor application.
Displays and allows you to edit on-
chip memory. In-System Memory Content
Editor
You want to prototype a front
panel with virtual buttons for your
FPGA design. Provides a way to drive and sample
logic values to and from internal
nodes using the JTAG interface. In-System Sources and Probes
You want to generate a large set
of test vectors and send them to
your device over the JTAG port to
functionally verify your design
running in hardware. Opens the JTAG interface so that you
can develop your own custom
applications. Virtual JTAG Interface
Related Information
System Debugging Tools Overview
Applications of the Virtual JTAG Megafunction
You can instantiate single or multiple instances of the Virtual JTAG megafunction in your HDL code. During
synthesis, the Quartus II software assigns unique IDs to each instance, so that each instance is accessed
individually. You can instantiate up to 128 instances of the Virtual JTAG megafunction. The figure below
shows a typical application in a design with multiple instances of the megafunction.
Figure 1: Application Example
Logic
Logic
JTAG
sld_virtual_jtag
sld_virtual_jtag
tck
tms
trst
tdi
tdo
The SLD hub automatically arbitrates between multiple applications that share a single JTAG resource.
Therefore, you can use the megafunction in tandem with other on-chip debugging applications, such as the
SignalTap II Logic Analyzer, to increase debugging visibility. You can also use the megafunction to provide
Altera Corporation Virtual JTAG Megafunction (sld_virtual_jtag)
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3 Applications of the Virtual JTAG Megafunction
UG-SLDVRTL
2014.03.19