Altera Virtual JTAG IP Core - Manual (Page 15)

Figure 8: Block Diagram of a Design with a Single Virtual JTAG Instantiation
Inferred by Instantiation
of Megafunction
Glue Logic between VJI and User Design
(Created by Designer)
Original Design
Application
Logic
SLD
Hub
VJI Megafunction
Instance
IR
JTAG TAP
Controller
TDI
TDO
TMS
TCK
TRST
TMS & Decoded
State Signals
IR_in
TDI
TDO
Input Vector 1
Input Vector 2
Input Vector n VDR
Chain
1
VDR
Chain
2
VDR
Chain
n
Simulation Model
The virtual JTAG megafunction contains a functional simulation model that provides stimuli that mimic
VIR and VDR shifts. You can configure the stimuli using the MegaWizard Plug-In Manager. You can use
this simulation model for functional verification only, and the operation of the SLD hub and the SLD
node-to-hub interface is not provided in this simulation model.
Run-Time Communication with the Virtual JTAG Megafunction
The Tcl API for the Virtual JTAG megafunction consists of a set of commands for accessing the VIR and
VDR of each virtual JTAG instance.
These commands contain the underlying drivers for accessing an Altera programming cable and for issuing
shift transactions to each VIR and VDR. The table below provides the Tcl commands in the
quartus_stp
executable that you can use with the Virtual JTAG megafunction, and are intended for designs that use a
custom controller to drive the JTAG chain.
Each instantiation of the Virtual JTAG megafunction includes an instance index. All instances are sequentially
numbered and are automatically provided by the Quartus II software. The instance index starts at instance
index
0
. The VIR and VDR shift commands described in the table decode the instance index and provide
an address to the SLD hub for each megafunction instance. You can override the default index provided by
the Quartus II software during configuration of the megafunction.
The table below provides the Tcl commands in the quartus_stp executable that you can use with the Virtual
JTAG megafunction, and are intended for designs that use a custom controller to drive the JTAG chain.
Altera Corporation Virtual JTAG Megafunction (sld_virtual_jtag)
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15 Simulation Model
UG-SLDVRTL
2014.03.19