X5328/X5329
Characteristics subject to change without notice.
6 of 21
REV 1.1.1 3/6/01
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The Write Enable Latch (WEL) bit indicates the Status
of the Write Enable Latch. When WEL = 1, the latch is
set HIGH and when WEL = 0 the latch is reset LOW.
The WEL bit is a volatile, read only bit. It can be set by
the WREN instruction and can be reset by the WRDS
instruction.
The block lock bits, BL0 and BL1, set the level of block
lock protection. These nonvolatile bits are programmed
using the WRSR instruction and allow the user to pro-
tect one quarter, one half, all or none of the EEPROM
array. Any portion of the array that is block lock pro-
tected can be read but not written. It will remain pro-
tected until the BL bits are altered to disable block lock
protection of that portion of memory.
The FLAG bit shows the status of a volatile latch that can
be set and reset by the system using the SFLB and
RFLB instructions. The Flag bit is automatically reset
upon power up.
The nonvolatile WPEN bit is programmed using the
WRSR instruction. This bit works in conjunction with the
WP pin to provide an In-Circuit Programmable ROM func-
tion (Table 2). WP is LOW and WPEN bit programmed
HIGH disables all Status Register Write Operations.
In Circuit Programmable ROM Mode
This mechanism protects the block lock and Watchdog
bits from inadvertent corruption.
In the locked state (
Programmable ROM Mode) the WP
pin is LOW and the nonvolatile bit WPEN is “1”. This
mode disables nonvolatile writes to the device’s Status
Register.
Setting the WP pin LOW while WPEN is a “1” while an
internal write cycle to the Status Register is in progress
will not stop this write operation, but the operation dis-
ables subsequent write attempts to the Status Register.
When WP is HIGH, all functions, including nonvolatile
writes to the Status Register operate normally.
Setting the WPEN bit in the Status Register to “0”
blocks the WP pin function, allowing writes to the Sta-
tus Register when WP is HIGH or LOW. Setting the
WPEN bit to “1” while the WP pin is LOW activates the
Programmable ROM mode, thus requiring a change in
the WP pin prior to subsequent Status Register
changes. This allows manufacturing to install the
device in a system with WP pin grounded and still be
able to program the Status Register. Manufacturing can
then load Configuration data, manufacturing time and
other parameters into the EEPROM, then set the por-
tion of memory to be protected by setting the block lock
bits, and finally set the “OTP mode” by setting the
WPEN bit. Data changes now require a hardware
change.
Status Register Bits
BL1
0
0
1
1
Array Addresses Protected
X5328/X5329
None
$0C00–$0FFF
$0800–$0FFF
$0000–$0FFF
BL0
0
1
0
1
Figure 5. Read EEPROM Array Sequence
0
1
2
3
4
5
6
7
8
9
10
20 21 22 23 24 25
26 27 28 29 30
7
6
5
4
3
2
1
0
Data Out
CS
SCK
SI
SO
MSB
High Impedance
Instruction
16 Bit Address
15 14 13
3
2
1
0