WM71000-NBSD-DA Ramtron, WM71000-NBSD-DA Datasheet - Page 12

• Manufacturer Part Number: WM71000-NBSD-DA
• Description: RFID Transponder AFE Chip (No Memory) Gen-2 RFID Access
• Manufacturer: Ramtron

Specifications of WM71000-NBSD-DA

• Mounting Style: SMD/SMT
• Package / Case: DFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

WORKING STORED ADDRESS
Rev. 1.3
Apr. 2011
Wrap Enable: Asserting the WRPEN control bit to a logic one enables the USER memory wrapping feature.
The wrap enable feature allows the stored address pointer to wrap back to the factory-set initial stored address
value of 0x006. In this manner, the WM710xx memory acts as a circular buffer. Clearing the WRPEN control
bit disables wrapping resulting in a write-once memory. In this case, when the Working Stored Address
reaches the end of user memory, no additional unaddressed write cycles will be possible. The WRPEN and
AUTOLOCK control bits are mutually exclusive – only one of the two control bits may be asserted at any
given time.
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 WM710xx 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.
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 12 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.
13:11
LCK
Bit
9:0
15
14
10
Table 6: Working Stored Address – Bit Definitions
PLCK
Mnemonic
LOCK
PERMALOCK
RFU
INITEN
ADDR
RFU
Figure 11. Working Stored Address Register
Function
Memory locking of this register.
When asserted to a logic ‘1’, sets the contents of the Initial Stored
Address register with the value defined in the 10-bit address field in bits
9 through 0 written to this register using a Gen2 write instruction.
Working stored address pointer
Reserved for future use
INIT
EN
LOCK
0
0
1
1
PERMALOCK
0
1
0
1
WM710xx – Secure F-RAM with Gen-2 RFID
DESCRIPTION
Register unlocked
Register permanently unlocked
Register writeable only from the
SECURED state
Register permanently locked
ADDR[9:0]
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Initial
Value
006
0
0
0
0