EP2C8T144I8N Datasheet, PDF (437/470 Pages) Altera Corporation – Cyclone II Device Handbook, Volume 1

IEEE 1149.1 (JTAG) Boundary-Scan Testing for Cyclone II Devices
During the capture phase, multiplexers preceding the capture registers
select the active device data signals. This data is then clocked into the
capture registers. The multiplexers at the outputs of the update registers
also select active device data to prevent functional interruptions to the
device. During the shift phase, the boundary-scan shift register is formed
by clocking data through capture registers around the device periphery,
then out of the TDO pin. The device can simultaneously shift new test data
into TDI and replace the contents of the capture registers. During the
update phase, data in the capture registers is transferred to the update
registers. This data can then be used in the EXTEST instruction mode. See
“EXTEST Instruction Mode” on page 14–11 for more information.
Figure 14–9 shows the SAMPLE/PRELOAD waveforms. The
SAMPLE/PRELOAD instruction code is shifted in through the TDI pin. The
TAP controller advances to the CAPTURE_DR state, then to the SHIFT_DR
state, where it remains if TMS is held low. The data that was present in the
capture registers after the capture phase is shifted out of the TDO pin. New
test data shifted into the TDI pin appears at the TDO pin after being
clocked through the entire boundary-scan register. Figure 14–9 shows
that the instruction code at TDI does not appear at the TDO pin until after
the capture register data 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.
Figure 14–9. SAMPLE/PRELOAD Shift Data Register Waveforms
TCK
TMS
TDI
TDO
SHIFT_IR
TAP_STATE
EXIT1_IR SELECT_DR
Instruction Code
UPDATE_IR CAPTURE_DR
Data stored in
boundary-scan
register is shifted
out of TDO.
SHIFT_DR
After boundary-scan EXIT1_DR
register data has been _{UPDATE_DR}
shifted out, data
entered into TDI will
shift out of TDO.
Altera Corporation
February 2007
EXTEST Instruction Mode
The EXTEST instruction mode is used to check external pin connections
between devices. Unlike the 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, opens and shorts can be detected at pins
of any device in the scan chain.
14–11
Cyclone II Device Handbook, Volume 1