WM72016 – Secure F-RAM with Gen-2 RFID and Serial Port

Rev. 1.4

May 2011

Page 15 of 32

INITIAL STORED ADDRESS

The Initial Stored Address is a preset address pointer that is loaded into the Working Stored Address when a

memory wrap occurs after an unaddressed write command is executed. A memory wrap only occurs if the

WRPEN control bit is asserted to a logic one and the AUTOLOCK control bit is cleared to a logic zero in the

Control/Status register and the Working Stored Address points to the last free memory location in the USER

memory bank (last memory location depends on the set block size).

The contents of the Initial Stored Address may be altered by setting the INITEN bit to a logic one through a

Gen2 write cycle to the Working Stored Address register – refer to Table 6 above. When the INITEN control

bit is set during a write cycle, the contents of the Working Stored Address register in USER memory 0x003 are

not affected.

Use of an Initial Stored Address register provides flexibility when using the wrap enable feature of WM72016.

It may be set to the start of USER memory, allowing the entire USER memory bank to be utilized.

Alternatively, it may be set to a higher memory address within the USER memory bank. This mechanism

would provide for a static USER memory bank and a dynamic USER memory bank as shown in Figure 16

below. In the example shown in Figure 16, the Working Stored Address points to address 0x3F8 after having

written user_log_data[n] with an unaddressed write command. The subsequent unaddressed write cycle will

increment (wrap) the Working Stored Address to the value defined by the Initial Stored Address, defined in this

example as 0x000A, and write the value user_log_data[n+1] to USER memory bank 0x00A, over-writing the

previous data contents user_log_data[0]. In the example shown, four memory locations are used for static

memory, or memory that will not be over-written when a wrap condition has occurred.