Digilent 410-087P-KIT - Manual (Page 129)

Spartan-3E Starter Kit Board User Guide www.xilinx.com 129
UG230 (v1.0) March 9, 2006
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Chapter 17
DS2432 1-Wire SHA-1 EEPROM
The Spartan-3E Starter Kit board includes a Maxim DS2432 serial EEPROM with an
integrated SHA-1 engine. As shown in
Figure 17-1 , the DS2432 EEPROM uses the Maxim
1-Wire interface, which as the name implies, cleverly uses a single wire for power and
serial communication.
The DS2432 EEPROM offers one of many possible means to copy-protect the FPGA
configuration bitstream, making cloning difficult. Xilinx application note XAPP780, listed
under
“Related Resources” provides one possible implementation method.
UCF Location Constraints
Figure 17-2 provides the UCF constraints for the FPGA connections to the DS2432 SHA-1
EEPROM, including the I/O pin assignment and the I/O standard used.
Related Resources
• Maxim DS2432 1-Wire EEPROM with SHA-1 Engine
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2914
• XAPP780: FPGA IFF Copy Protection Using Dallas Semiconductor/Maxim DS2432 Secure
EEPROMs
http://www.xilinx.com/bvdocs/appnotes/xapp780.pdf
Figure 17-1: SHA-1 EEPROM
Maxim DS2432
SHA-1 EEPROM
(U4)
DS_WIRE
Spartan-3E FPGA
GND
3.3V
UG230_c17_01_030906
Figure 17-2: UCF Location Constraints for DS2432 SHA-1 EEPROM
NET "DS_WIRE" LOC = "U4" | IOSTANDARD = LVCMOS33 | SLEW = SLOW | DRIVE = 8 ;