13–14
Chapter 13: IEEE 1149.1 (JTAG) Boundary-Scan Testing for MAX II Devices
IEEE Std. 1149.1 BST Operation Control
IDCODE Instruction Mode
The IDCODEinstruction mode is used to identify the devices in an IEEE Std. 1149.1
chain. When IDCODEis selected, the device identification register is loaded with the
32-bit vendor-defined identification code. The device ID register is connected between
the TDIand TDOports, and the device IDCODEis shifted out.
1
The IDCODEfor MAX II devices are listed in the JTAG and In-System Programmability
chapter in the MAX II Device Handbook.
USERCODE Instruction Mode
The USERCODE instruction mode is used to examine the user electronic signature
(UES) within the devices along an IEEE Std. 1149.1 chain. When this instruction is
selected, the device identification register is connected between the TDIand TDO
ports. The user-defined UES is shifted into the device ID register in parallel from the
32-bit USERCODEregister. The UES is then shifted out through the device ID register.
The USERCODEinformation is available to the user only after the device is configured
successfully.
The non-volatile USERCODEdata is written to the configuration flash memory (CFM)
block and then written to the SRAM at power-up. The USERCODEinstruction reads
the data values from the SRAM. When using real-time ISP to update the CFM block
and write new USERCODEdata, executing the USERCODEinstruction returns the
current running design’s USERCODE(stored in the SRAM), not the new USERCODE
data. The new design’s USERCODE, stored in the CFM, can only be read back correctly
if a power cycle or forced SRAM download has transpired after the real-time ISP
update.
In the Quartus II software, there is an Auto Usercode feature where you can choose to
use the checksum value of a programming file as the JTAG user code. If selected, the
checksum will be automatically loaded to the USERCODEregister. On the Assignments
menu, click Device. In the Device dialog box, click Device and Pin Options and click
the General tab. Turn on Auto Usercode.
CLAMP Instruction Mode
The CLAMPinstruction mode is used to allow the state of the signals driven from the
pins to be determined from the boundary-scan register while the bypass register is
selected as the serial path between the TDIand TDOports. The state of all signals
driven from the output pins will be completely defined by the data held in the
boundary-scan register. However, CLAMP will not override the I/O weak pull-up
resistor or the I/O bus hold if you have any of them selected.
HIGHZ Instruction Mode
The HIGHZinstruction mode is used to set all of the user I/O pins to an inactive drive
state. These pins are tri-stated until a new JTAG instruction is executed. When this
instruction is selected, the bypass register is connected between the TDIand TDO
ports. HIGHZwill not override the I/O weak pull-up resistor or the I/O bus hold if
you have any of them selected.
MAX II Device Handbook
© October 2008 Altera Corporation
ALTERA [ ALTERA CORPORATION ]
