Altera Virtual JTAG IP Core Manual de usuario descargar pdf (Pagina 17)

Each device_virtual_ir_shift command issues a USER1 instruction to the JTAG Instruction Register

followed by a DR shift containing the VIR value provided by the ir_value argument prepended by address

bits to target the correct SLD node instance.

Use the -no_captured_ir_value argument if you do not care about shifting out the contents of the

current VIR value. Enabling this argument increases the speed of the VIR shift transaction by

eliminating a command cycle within the underlying transaction.

Note:

Similarly, each device_virtual_dr_shift command issues a USER0 instruction to the JTAG Instruction

commands return the underlying JTAG transactions with the show_equivalent_device_ir_dr_shift

option set.

The device_virtual_ir_shift takes the ir_value argument as a numeric value. The

device_virtual_dr_shift takes the dr_value argument by either a binary string or a hexadecimal

string. Do not use numeric values for the device_virtual_dr_shift.

Note:

Running a DR Shift Operation Through a Virtual JTAG Chain

A simple DR shift operation through a virtual JTAG chain using an Altera download cable consists of the

following steps:

1. Query for the Altera programming cable and select the active cable.

2. Target the desired device in the JTAG chain.

3. Obtain a device lock for exclusive communication to the device.

4. Perform a VIR shift.

5. Perform a VDR shift.

6. Release exclusive link with the device with the device_unlock command.

7. Close communication with the device with the close_device command.

Run-Time Communication without Using an Altera Programming Cable

The Virtual JTAG megafunction Tcl API requires an Altera programming cable. Designs that use a custom

controller to drive the JTAG chain directly must issue the correct JTAG IR/DR transactions to target the

Virtual JTAG megafunction instances. The address values and register length information for each Virtual

JTAG megafunction instance are provided in the compilation reports.

The following figure shows the compilation report for a Virtual JTAG megafunction Instance. The following

table describes each column in the Virtual JTAG Settings compilation report.

Altera Corporation

Virtual JTAG Megafunction (sld_virtual_jtag)

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Running a DR Shift Operation Through a Virtual JTAG Chain

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2014.03.19

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Altera Virtual JTAG IP Core Manual de usuario Pagina 17