CAT25320 Datasheet, PDF (5/16 Pages) Catalyst Semiconductor – 32-Kb SPI Serial CMOS EEPROM

CAT25320
STATUS REGISTER
The Status Register, as shown in Table 2, contains a
number of status and control bits.
The ¯R¯D¯Y¯ (Ready) bit indicates whether the device is
busy with a write operation. This bit is automatically
set to 1 during an internal write cycle, and reset to 0
when the device is ready to accept commands. For
the host, this bit is read only.
The WEL (Write Enable Latch) bit is set/reset by the
WREN/WRDI commands. When set to 1, the device is
in a Write Enable state and when set to 0, the device
is in a Write Disable state.
The BP0 and BP1 (Block Protect) bits determine
which blocks are currently write protected. They are
set by the user with the WRSR command and are
Table 2. Status Register
7
6
5
4
WPEN
0
0
0
non-volatile. The user is allowed to protect a quarter,
one half or the entire memory, by setting these bits
according to Table 3. The protected blocks then
become read-only.
The WPEN (Write Protect Enable) bit acts as an
enable for the ¯W¯P¯ pin. Hardware write protection is
enabled when the ¯W¯P¯ pin is low and the WPEN bit
is 1. This condition prevents writing to the status
register and to the block protected sections of
memory. While hardware write protection is active,
only the non-block protected memory can be written.
Hardware write protection is disabled when the ¯W¯P¯
pin is high or the WPEN bit is 0. The WPEN bit, ¯W¯P¯
pin and WEL bit combine to either permit or inhibit
Write operations, as detailed in Table 4.
3
2
1
0
BP1
BP0
WEL
¯R¯D¯Y¯
Table 3. Block Protection Bits
Status Register Bits
BP1
BP0
0
0
0
1
1
0
1
1
Array Address Protected
None
0C00-0FFF
0800-0FFF
0000-0FFF
Protection
No Protection
Quarter Array Protection
Half Array Protection
Full Array Protection
Table 4. Write Protect Conditions
WPEN
¯W¯P¯
0
X
0
X
1
Low
1
Low
X
High
X
High
WEL
0
1
0
1
0
1
Protected
Blocks
Protected
Protected
Protected
Protected
Protected
Protected
Unprotected
Blocks
Protected
Writable
Protected
Writable
Protected
Writable
Status
Register
Protected
Writable
Protected
Protected
Protected
Writable
© 2007 Catalyst Semiconductor, Inc.
5
Characteristics subject to change without notice
Doc. No. 1111 Rev. E