Chapter 10: JTAG Boundary-Scan Testing for Cyclone IV Devices
10–5
I/O Voltage Support in a JTAG Chain
December 2013
Altera Corporation
EXTEST_PULSE
The instruction code for
EXTEST_PULSE
is 0010001111. The
EXTEST_PULSE
instruction
generates three output transitions:
■
Driver drives data on the falling edge of
TCK
in UPDATE_IR/DR.
■
Driver drives inverted data on the falling edge of
TCK
after entering the
RUN_TEST/IDLE state.
■
Driver drives data on the falling edge of
TCK
after leaving the RUN_TEST/IDLE
state.
1
If you use DC-coupling on HSSI signals, you must execute the
EXTEST
instruction. If
you use AC-coupling on HSSI signals, you must execute the
EXTEST_PULSE
instruction. AC-coupled and DC-coupled HSSI are only supported in
post-configuration mode.
EXTEST_TRAIN
The instruction code for
EXTEST_TRAIN
is 0001001111. The
EXTEST_TRAIN
instruction
behaves the same as the
EXTEST_PULSE
instruction with one exception. The output
continues to toggle on the
TCK
falling edge as long as the test access port (TAP)
controller is in the RUN_TEST/IDLE state.
1
These two instruction codes are only supported in post-configuration mode for
Cyclone IV GX devices.
1
When you perform JTAG boundary-scan testing before configuration, the
nCONFIG
pin
must be held low.
I/O Voltage Support in a JTAG Chain
A Cyclone IV device operating in BST mode uses four required pins:
TDI
,
TDO
,
TMS
,
and
TCK
. The
TDO
output pin and all JTAG input pins are powered by the V
CCIO
power
supply of I/O Banks (I/O Bank 9 for Cyclone IV GX devices and I/O Bank 1 for
Cyclone IV E devices).
A JTAG chain can contain several different devices. However, you must use caution if
the chain contains devices that have different V
CCIO
levels. The output voltage level of
the
TDO
pin must meet the specification of the
TDI
pin it drives. For example, a device
with a 3.3-V
TDO
pin can drive a device with a 5.0-V
TDI
pin because 3.3 V meets the
minimum TTL-level V
IH
for the 5.0-V
TDI
pin.
1
For multiple devices in a JTAG chain with the 3.0-V/3.3-V I/O standard, you must
connect a 25-
series resistor on a
TDO
pin driving a
TDI
pin.
You can also interface the
TDI
and
TDO
lines of the devices that have different V
CCIO
levels by inserting a level shifter between the devices. If possible, the JTAG chain
should have a device with a higher V
CCIO
level driving a device with an equal or
lower V
CCIO
level. This way, a level shifter may be required only to shift the
TDO
level
to a level acceptable to the JTAG tester.
Summary of Contents for Cyclone IV
Page 10: ...x Chapter Revision Dates Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 14: ...I 2 Section I Device Core Cyclone IV Device Handbook March 2016 Altera Corporation Volume 1...
Page 274: ...vi Contents Cyclone IV Device Handbook February 2015 Altera Corporation Volume 2...
Page 440: ...iv Contents Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
Page 442: ...vi Chapter Revision Dates Cyclone IV Device Handbook December 2016 Altera Corporation Volume 3...
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