Chapter 13: IEEE 1149.1 (JTAG) Boundary-Scan Testing for MAX II Devices
13–13
IEEE Std. 1149.1 BST Operation Control
EXTESTselects data differently than SAMPLE/PRELOAD. EXTESTchooses data from
the update registers as the source of the output and output enable signals. Once the
EXTESTinstruction code is entered, the multiplexers select the update register data;
thus, data stored in these registers from a previous EXTESTor SAMPLE/PRELOADtest
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 TDOduring the shift
phase. New test data can then be stored in the update registers during the update
phase.
The waveform diagram in Figure 13–11 resembles the SAMPLE/PRELOADwaveform
diagram, except that the instruction code for EXTESTis different. The data shifted out
of TDOconsists of the data that was present in the capture registers after the capture
phase. New test data shifted into the TDIpin appears at the TDOpin after being
clocked through the entire boundary-scan register.
Figure 13–11. EXTEST Shift Data Register Waveforms
TCK
TMS
TDI
TDO
SHIFT_IR
TAP_STATE
SHIFT_DR
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
BYPASS Instruction Mode
The BYPASSinstruction mode is activated with an instruction code made up of only
ones. The waveforms in Figure 13–12 show how scan data passes through a device
once the TAP controller is in the SHIFT_DRstate. In this state, data signals are clocked
into the bypass register from TDIon the rising edge of TCKand out of TDOon the
falling edge of the same clock pulse.
Figure 13–12. BYPASS Shift Data Register Waveforms
TCK
TMS
Bit 1
Bit 2
Bit 1
Bit 3
Bit 2
TDI
Bit n
TDO
SHIFT_IR
TAP_STATE
SHIFT_DR
SELECT_DR_SCAN
EXIT1_DR
UPDATE_DR
EXIT1_IR
Data shifted into TDI on
the rising edge of TCK is
shifted out of TDO on the
falling edge of the same
TCK pulse.
UPDATE_IR
CAPTURE_DR
Instruction Code
© October 2008 Altera Corporation
MAX II Device Handbook
ALTERA [ ALTERA CORPORATION ]
