ChipScope Pro Software and Cores User Guide
155
UG029 (v14.3) October 16, 2012
CseJtag Tcl Commands
::chipscope::csejtag_tap autodetect_chain
This subcommand attempts to automatically detect the composition of the JTAG chain.
The subcommand first obtains the number of devices and
IDCODE
values for devices in the
JTAG chain. The IR lengths are then determined for the devices in the JTAG chain that have
an
IDCODE
. The IR lengths for devices that do not have corresponding
IDCODE
s must be
assigned manually. Upon success, all pertinent device information is determined and set in
the session. Some IEEE 1149.1 non-compliant devices might not be compatible with this
subcommand and might cause the entire chain to be detected incorrectly or not at all.
Note:
The JTAG target must be locked by using the
::chipscope::csejtag_target lock
subcommand before calling this subcommand.
Syntax
::chipscope::csejtag_tap autodetect_chain handle algorithm
Arguments
Returns
An exception is thrown if the subcommand fails to detect the chain completely. In the case
of such an error, the devices in the JTAG chain must be detected and assigned manually.
Example
Attempt to automatically detect the chain using the default algorithm.
%::chipscope::csejtag_tap autodetect_chain $handle
$CSEJTAG_SCAN_DEFAULT
Back to list of all CseJtag Tcl Commands
Table 5-27:
Arguments for Subcommand ::chipscope::csejtag_tap
autodetect_chain
Argument
Type
Description
handle
Required
Handle to the session that is returned by
::chipscope::csejtag_session create
.
algorithm
Algorithm used to determine the composition of the JTAG
chain. Can be set to one of
{$CSEJTAG_SCAN_DEFAULT |
$CSEJTAG_SCAN_TLRSHIFT |
$CSEJTAG_SCAN_WALKING_ONES}
The
CSEJTAG_SCAN_WALKING_ONES
algorithm is:
•
Set each device into
BYPASS
by shifting long stream of 1's
into
IR
.
•
Shift
DR
pattern into
TDI
and wait for pattern on
TDO
. The
number of shifts determines the number of devices in the
JTAG chain.
•
Perform the
CSEJTAG_SCAN_TLRSHIFT
algorithm to get
IDCODE
s for each device.
The
CSEJTAG_SCAN_TLRSHIFT
algorithm is:
•
Navigate to
TLR
Shift out bits until all
IDCODE
s (or
BYPASS
bits) are read.