EP2S90F1020C5 Datasheet, PDF (707/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

IEEE 1149.1 (JTAG) Boundary-Scan Testing for Stratix II and Stratix II GX Devices
EXTEST selects data differently than SAMPLE/PRELOAD. EXTEST chooses
data from the update registers as the source of the output and output
enable signals. Once the EXTEST instruction code is entered, the
multiplexers select the update register data. Thus, data stored in these
registers from a previous EXTEST or SAMPLE/PRELOAD test cycle can be
forced 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. New test data can then be stored in the update registers
during the update phase.
The EXTEST waveform diagram in Figure 9–11 resembles the
SAMPLE/PRELOAD waveform diagram, except for the instruction code.
The data shifted out of TDO consists of the data that was present in the
capture registers after the capture phase. New test data shifted into the
TDI pin appears at the TDO pin after being clocked through the entire
boundary-scan register.
Figure 9–11. EXTEST 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.
BYPASS Instruction Mode
The BYPASS mode is activated when an instruction code of all ones is
loaded in the instruction register. The waveforms in Figure 9–12 show
how scan data passes through a device once the TAP controller is in the
SHIFT_DR state. In this state, data signals are clocked into the bypass
register from TDI on the rising edge of TCK and out of TDO on the falling
edge of the same clock pulse.
Altera Corporation
January 2008
9–15
Stratix II Device Handbook, Volume 2