8–14
Chapter 8: JTAG Boundary-Scan Testing in MAX V Devices
Boundary-Scan Test for Programmed Devices
levels, the devices can interface with each other. For example, a device with 3.3-V
VCCIO can drive to a device with 5.0-V VCCIO because 3.3 V meets the minimum VIH on
transistor-to-transistor logic (TTL)-level input for the 5.0-V VCCIO device. JTAG pins
on MAX V devices can support 1.5-, 1.8-, 2.5-, or 3.3-V input levels, depending on the
VCCIO voltage of I/O Bank 1.
f For more information about MultiVolt I/O support, refer to the MAX V Device
Architecture chapter.
You can interface the TDIand TDOlines of the JTAG pins of devices that have different
VCCIO levels by inserting a level shifter between the devices. If possible, the JTAG
chain must be built such that a device with a higher VCCIO level drives to a device with
an equal or lower VCCIO level. By building the JTAG chain in this manner, a level
shifter may be required only to shift the TDOlevel to a level acceptable to the JTAG
tester.
Figure 8–13 shows the JTAG chain of mixed voltages and how a level shifter is
inserted in the chain.
Figure 8–13. JTAG Chain of Mixed Voltages
Must be 5.0-V
Tolerant
Must be 3.3-V
Tolerant
TDI
5.0-V
3.3-V
2.5-V
V
V
V
CCIO
CCIO
CCIO
Tester
TDO
Level
1.5-V
11..88--VV
Shifter
V
VV
CCIO
CCCCIIOO
Shift TDO to Level
Accepted by Tester
if Necessary
Must be 1.8-V
Tolerant
Must be 2.5-V
Tolerant
Boundary-Scan Test for Programmed Devices
For a programmed device, the input buffers are turned off by default for I/O pins that
are set as output only in the design file. You cannot sample on the programmed device
output pins with the default boundary-scan description language (BSDL) file when
the input buffers are turned off.
For boundary-scan testing, you can set the Quartus II software to always enable the
input buffers on a programmed device so it behaves the same as an unprogrammed
device, allowing sample function on output pins in the design. This aspect can cause
slight increase in standby current as the unused input buffer is always on.
To enable the unused input buffers on a programmed device, follow these steps:
1. On the Assignments menu, click Settings.
2. Under Category, select Assembler.
3. Turn on Always Enable Input Buffers.
MAX V Device Handbook
December 2010 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
