Rainbow Electronics AT25F4096 - Manual (Page 8)

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AT25F4096 [Advance Information]
2454C–SEEPR–8/04
READ PRODUCT ID (RDID): The RDID instruction allows the user to read the manufac-
turer and product ID of the device. The first byte after the instruction will be the
manufacturer code (1FH = ATMEL), followed by the device code 64H.
WRITE STATUS REGISTER (WRSR): The WRSR instruction allows the user to select
one of five levels of protection for the AT25F4096. The AT25F4096 is divided into eight
sectors where the top 1/8, top quarter (1/4), top half (1/2), or all of the memory sectors
can be protected (locked out) from write. Any of the locked-out sectors will therefore be
READ only. The locked-out sector and the corresponding status register control bits are
shown in Table 4.
The four bits, BP0, BP1, BP2 and WPEN, are nonvolatile cells that have the same prop-
erties and functions as the regular memory cells (e.g., WREN, t
WC
, RDSR).
Note: 1. x = don’t care
The WRSR instruction also allows the user to enable or disable the Write Protect (WP)
pin through the use of the Write Protect Enable (WPEN) bit. Hardware write protection is
enabled when the WP pin is low and the WPEN bit is “1”. Hardware write protection is
disabled when either the WP pin is high or the WPEN bit is “0.” When the device is hard-
ware write protected, writes to the Status Register, including the Block Protect bits and
the WPEN bit, and the locked-out sectors in the memory array are disabled. Write is
only allowed to sectors of the memory which are not locked out. The WRSR instruction
is self-timed to automatically erase and program BP0, BP1, BP2 and WPEN bits. In
Table 3. Read Status Register Bit Definition
Bit Definition
Bit 0 (RDY)
Bit 0 = 0 (RDY) indicates the device is READY. Bit 0 = 1 indicates the
write cycle is in progress.
Bit 1 (WEN)
Bit 1 = 0 indicates the device is not WRITE ENABLED. Bit 1 = 1 indicates
the device is WRITE ENABLED.
Bit 2 (BP0) See Table 4.
Bit 3 (BP1) See Table 4.
Bit 4 (BP2) See Table 4.
Bits 5-6 are 0s when device is not in an internal write cycle.
Bit 7 (WPEN) See Table 5.
Bits 0-7 are 1s during an internal write cycle.
Table 4. Block Write Protect Bits
Level
Status Register Bits AT25F4096
BP2 BP1 BP0
Array Addresses
Locked Out Locked-out Sector(s)
0(none) 0 0 0 None None
1(1/8) 0 0 1 070000 - 07FFFF Sector 8
2(1/4) 0 1 0 060000 - 07FFFF Sector 7, 8
3(1/2) 0 1 1 040000 - 07FFFF Sector 5, 6, 7, 8
4(all) 1 x x 000000 - 07FFFF
All sectors
(1 - 8)