Document Number: 001-55720 Rev. *H Page 6 of 28
Preventing AutoStore
The AutoStore function is disabled by initiating an AutoStore
disable sequence. A sequence of read operations is performed
in a manner similar to the Software STORE initiation. To initiate
the AutoStore disable sequence, the following sequence of CE
or OE controlled read operations must be performed:
1. Read address 0x0E38 Valid READ
2. Read address 0x31C7 Valid READ
3. Read address 0x03E0 Valid READ
4. Read address 0x3C1F Valid READ
5. Read address 0x303F Valid READ
6. Read address 0x0B45 AutoStore Disable
The AutoStore is reenabled by initiating an AutoStore enable
sequence. A sequence of read operations is performed in a
manner similar to the Software RECALL initiation.
To initiate the AutoStore enable sequence, the following
sequence of CE
or OE controlled read operations must be
performed:
1. Read address 0x0E38 Valid READ
2. Read address 0x31C7 Valid READ
3. Read address 0x03E0 Valid READ
4. Read address 0x3C1F Valid READ
5. Read address 0x303F Valid READ
6. Read address 0x0B46 AutoStore Enable
If the AutoStore function is disabled or re-enabled, a manual
STORE operation (Hardware or Software) issued to save the
AutoStore state through subsequent power-down cycles. The
part comes from the factory with AutoStore enabled and 0x00
written in all cells.
Data Protection
The CY14B256KA protects data from corruption during low
voltage conditions by inhibiting all externally initiated STORE
and write operations. The low voltage condition is detected when
V
CC
is less than V
SWITCH
. If the CY14B256KA is in a write mode
(both CE
and WE are LOW) at power-up, after a RECALL or
STORE, the write is inhibited until the SRAM is enabled after
t
LZHSB
(HSB to output active). This protects against inadvertent
writes during power-up or brown out conditions.
Table 1. Mode Selection
CE WE OE
A
14
–A
0
[3]
Mode I/O Power
H X X X Not Selected Output High Z Standby
L H L X Read SRAM Output Data Active
L L X X Write SRAM Input Data Active
L H L 0x0E38
0x31C7
0x03E0
0x3C1F
0x303F
0x0B45
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Read SRAM
AutoStore
Disable
Output Data
Output Data
Output Data
Output Data
Output Data
Output Data
Active
[4]
L H L 0x0E38
0x31C7
0x03E0
0x3C1F
0x303F
0x0B46
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Read SRAM
AutoStore Enable
Output Data
Output Data
Output Data
Output Data
Output Data
Output Data
Active
[4]
L H L 0x0E38
0x31C7
0x03E0
0x3C1F
0x303F
0x0FC0
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Nonvolatile
STORE
Output Data
Output Data
Output Data
Output Data
Output Data
Output High Z
Active I
CC2
[4]
L H L 0x0E38
0x31C7
0x03E0
0x3C1F
0x303F
0x0C63
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Read SRAM
Nonvolatile
RECALL
Output Data
Output Data
Output Data
Output Data
Output Data
Output High Z
Active
[4]
Notes
3. While there are 15 address lines on the CY14B256KA, only the lower 14 are used to control software modes.
4. The six consecutive address locations must be in the order listed. WE
must be HIGH during all six cycles to enable a nonvolatile cycle.
(19 pages)
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