CAT25640 CATALYST [Catalyst Semiconductor], CAT25640 Datasheet - Page 5

• Manufacturer Part Number: CAT25640
• Description: 64-Kb SPI Serial CMOS EEPROM
• Manufacturer: CATALYST [Catalyst Semiconductor]

STATUS REGISTER
The Status Register, as shown in Table 2, contains a
number of status and control bits.
The RDY
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
Table 3. Block Protection Bits
Table 4. Write Protect Conditions
© Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
WPEN
¯¯¯¯ (Ready) bit indicates whether the device is
WPEN
7
BP1
Status Register Bits
0
0
1
1
X
X
0
0
1
1
6
0
BP0
0
1
0
1
High
High
Low
Low
¯¯¯
WP
X
X
5
0
Array Address Protected
WEL
0
1
0
1
0
1
4
0
1800-1FFF
1000-1FFF
0000-1FFF
None
5
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 WP
enabled when the WP
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 WP
pin is high or the WPEN bit is 0. The WPEN bit, WP
pin and WEL bit combine to either permit or inhibit
Write operations, as detailed in Table 4.
Protected
Protected
Protected
Protected
Protected
Protected
Protected
BP1
Blocks
3
¯¯¯ pin. Hardware write protection is
BP0
¯¯¯ pin is low and the WPEN bit
2
Unprotected
Protected
Protected
Protected
Writable
Writable
Writable
Blocks
Quarter Array Protection
Half Array Protection
Full Array Protection
No Protection
Protection
WEL
1
CAT25640
Doc. No. MD-1128 Rev. B
Protected
Protected
Protected
Protected
Register
Writable
Writable
Status
¯¯¯¯
RDY
0
¯¯¯
¯¯¯