8–10
Chapter 8: JTAG Boundary-Scan Testing in MAX V Devices
IEEE Std. 1149.1 BST Operation Control
Figure 8–9 shows that the test data that shifted into TDIdoes not appear at the TDOpin
until after the capture register data that is shifted out. If TMSis held high on two
consecutive TCKclock cycles, the TAP controller advances to the UPDATE_DRstate for
the update phase.
If you enable the device output enable feature but the DEV_OEpin is not asserted
during boundary-scan testing, the output enable boundary-scan registers of the BSCs
capture data from the core of the device during SAMPLE/PRELOAD. These values are not
high impedance, although the I/O pins are tri-stated.
Figure 8–9 shows the SAMPLE/PRELOADwaveforms.
Figure 8–9. SAMPLE/PRELOAD Shift Data Register Waveforms
TCK
TMS
TDI
TDO
SHIFT_IR
SHIFT_DR
TAP_STATE
EXIT1_IR
UPDATE_IR
EXIT1_DR
SELECT_DR_SCAN
After boundry-scan
register data has been
shifted out, data
entered into TDI will
shift out of TDO.
Data stored in
boundary-scan
register is shifted
out of TDO.
Instruction Code
UPDATE_DR
CAPTURE_DR
EXTEST Instruction Mode
Use EXTESTinstruction mode to check the external pin connections between devices.
Unlike SAMPLE/PRELOADmode, EXTESTallows test data to be forced onto the pin
signals. By forcing known logic high and low levels on output pins, you can detect
opens and shorts at pins of any device in the scan chain.
EXTESTselects data differently than SAMPLE/PRELOAD. EXTESTchooses data from the
update registers as the source of the output and output enable signals. After the
EXTESTinstruction code is entered, the multiplexers select the update register data;
thus, you can force the data stored in these registers from a previous EXTESTor
SAMPLE/PRELOADtest cycle onto the pin signals. In the capture phase, the results of this
test data are stored in the capture registers and then shifted out of TDOduring the shift
phase. You can store the new test data in the update registers during the update
phase.
MAX V Device Handbook
December 2010 Altera Corporation
INTEL [ INTEL ]
