ChipScope Pro Software and Cores User Guide
159
UG029 (v14.3) October 16, 2012
CseJtag Tcl Commands
::chipscope::csejtag_tap get_irlength
This subcommand retrieves the instruction register (IR) length of a device in the current
JTAG chain. The IR length is used to determine the amount of padding required to shift an
instruction into a device register. TAP shift and navigate operations do not work until all
devices have the IR lengths set up correctly. The
::chipscope::csejtag_tap
autodetect_chain
subcommand automatically sets up IR lengths for all devices in the
chain that support the
IDCODE
command.
Note:
The JTAG target must be locked by using the
::chipscope::csejtag_target lock
subcommand before calling this subcommand. Also, the device count must be set prior to calling this
subcommand using the
::chipscope::csejtag_tap set_device_count
.
Syntax
::chipscope::csejtag_tap get_irlength handle deviceIndex
Arguments
Returns
The length of the IR for the device.
An exception is thrown if the subcommand fails.
Example
Get the IR length of the device at index 0.
%set irLength [::chipscope::csejtag_tap get_irlength $handle 0]
Back to list of all CseJtag Tcl Commands
Table 5-31:
Arguments for Subcommand ::chipscope::csejtag_tap get_irlength
Argument
Type
Description
handle
Required
Handle to the session that is returned by
::chipscope::csejtag_session create
.
deviceIndex
Device index (0 to
n
-1) in the
n
-length JTAG chain.
