WM72016 – Secure F-RAM with Gen-2 RFID and Serial Port
Auto Lock Enable:
Asserting the AUTOLOCK control bit to a logic one enables memory locking of the USER
memory span between the start of USER memory and the Working Stored Address. The AUTOLOCK and
WRPEN control bits are mutually exclusive – only one of the two control bits may be asserted at any given
time. The automatic locking feature can only be used when AUTOINCR is asserted to a logic one.
Auto Increment:
Asserting AUTOINCR control bit to a logic one enables the Working Stored Address
increment function. Upon receiving an unaddressed write cycle, the WM72016 increments the pointer stored
in the Working Stored Address register to point to the next free memory location then writes the cover-coded
data word to the respective memory location. This functionality removes any requirement for a RFID
interrogator to determine where free USER memory is located and manipulating the memory pointer itself.
WORKING STORED ADDRESS
To better utilize the F-RAM’s fast write capability, memory has been architected using an optional Working
Stored Address register. The stored address function enables automation of the storage of large blocks of user
data, such as pedigree or tracking information. This feature enables a RFID interrogator the ability to use a
standard Gen2 WRITE command using a designated address of 0x3FFF (0xFF7F EBV-formatted) as a redirect
pointer to use the contents of the Working Stored Address register – this is referred to as an
unaddressed write
(UNADDR_WRITE).
The Working Stored Address is a USER memory address pointer addressing the last
unaddressed memory write cycle as shown in Figure 5 below. The Working Stored Address is a read/write
register located in USER memory, address 0x003. It may be manually updated by simply writing to USER
memory address 0x003 or automatically increment when the AUTOINCR control bit in the Control/Status
register is asserted to a logic one and an unaddressed write command is received.
Figure 5. USER Memory Bank: Working Stored Address Register
Rev. 1.2
Sept. 2010
Page 9 of 21
RAMTRON [ RAMTRON INTERNATIONAL CORPORATION ]
