5M80ZE64I5N Datasheet, PDF (158/166 Pages) Altera Corporation – MAX V Device Handbook

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 TDI does not appear at the TDO pin
until after the capture register data that is shifted out. If TMS is held high on two
consecutive TCK clock cycles, the TAP controller advances to the UPDATE_DR state for
the update phase.
If you enable the device output enable feature but the DEV_OE pin 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/PRELOAD waveforms.
Figure 8–9. SAMPLE/PRELOAD Shift Data Register Waveforms
TCK
TMS
TDI
TDO
SHIFT_IR
TAP_STATE
Instruction Code
EXIT1_IR SELECT_DR_SCAN
Data stored in
UPDATE_IR
CAPTURE_DR ^{boundary-scan}
register is shifted
out of TDO.
SHIFT_DR
After boundry-scan
register data has been
shifted out, data
entered into TDI will
shift out of TDO.
EXIT1_DR
UPDATE_DR
EXTEST Instruction Mode
Use EXTEST instruction mode to check the external pin connections between devices.
Unlike SAMPLE/PRELOAD mode, EXTEST allows 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.
EXTEST selects data differently than SAMPLE/PRELOAD. EXTEST chooses data from the
update registers as the source of the output and output enable signals. After the
EXTEST instruction code is entered, the multiplexers select the update register data;
thus, you can force the data stored in these registers from a previous EXTEST or
SAMPLE/PRELOAD test 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 TDO during 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