Description
Instruction Code
JTAG Instruction
• Allows you to test the external
circuit and board-level intercon-
nects by forcing a test pattern at the
output pins, and capturing the test
results at the input pins. Forcing
known logic high and low levels on
output pins allows you to detect
opens and shorts at the pins of any
device in the scan chain.
• The high-impedance state of
EXTEST
is overridden by bus hold and weak
pull-up resistor features.
00 0000 1111
EXTEST
Places the 1-bit bypass register between
the
TDI
and
TDO
pins. During normal
device operation, the 1-bit bypass
register allows the BST data to pass
synchronously through the selected
devices to adjacent devices.
11 1111 1111
BYPASS
• Examines the user electronic
signature (UES) within the devices
along a JTAG chain.
• Selects the 32-bit
USERCODE
register
and places it between the
TDI
and
TDO
pins to allow serial shifting of
USERCODE
out of
TDO
.
• The UES value is set to default value
before configuration and is only
user-defined after the device is
configured.
00 0000 0111
USERCODE
• Identifies the devices in a JTAG
chain. If you select
IDCODE
, the
device identification register is
loaded with the 32-bit
vendor-defined identification code.
• Selects the
IDCODE
register and
places it between the
TDI
and
TDO
pins to allow serial shifting of
IDCODE
out of
TDO
.
•
IDCODE
is the default instruction at
power up and in the
TAP RESET
state. Without loading any instruc-
tions, you can go to the
SHIFT_DR
state and shift out the JTAG device
ID.
00 0000 0110
IDCODE
JTAG Boundary-Scan Testing in Cyclone V Devices
Altera Corporation
CV-52009
Supported JTAG Instruction
9-4
2014.01.10