A
PPLICATION
N
OTE
A V A I L A B L E
AN95 • AN103 • AN107
16K/64K/128K
X84161/641/129
µ
Port Saver EEPROM
DESCRIPTION
MPS
™
EEPROM
FEATURES
• Up to 10MHz data transfer rate
• 25ns Read Access Time
• Direct Interface to Microprocessors and
Microcontrollers
—Eliminates I/O port requirements
—No interface glue logic required
—Eliminates need for parallel to serial converters
• Low Power CMOS
—1.8V–3.6V, 2.5V–5.5V and 5V
±10%
Versions
—Standby Current Less than 1µA
—Active Current Less than 1mA
• Byte or Page Write Capable
—32-Byte Page Write Mode
• Typical Nonvolatile Write Cycle Time: 2ms
• High Reliability
—100,000 Endurance Cycles
—Guaranteed Data Retention: 100 Years
The
µ
Port Saver memories need no serial ports or spe-
cial hardware and connect to the processor memory bus.
Replacing bytewide data memory, the
µ
Port Saver uses
bytewide memory control functions, takes a fraction of
the board space and consumes much less power.
Replacing serial memories, the
µ
Port Saver provides all
the serial benefits, such as low cost, low power, low volt-
age, and small package size while releasing I/Os for
more important uses.
The
µ
Port Saver memory outputs data within 25ns of an
active read signal. This is less than the read access time
of most hosts and provides “no-wait-state” operation.
This prevents bottlenecks on the bus. With rates to 10
MHz, the
µ
Port Saver supplies data faster than required
by most host read cycle specifications. This eliminates
the need for software NOPs.
The
µ
Port Saver memories communicate over one line of
the data bus using a sequence of standard bus read and
write operations. This “bit serial” interface allows the
µ
Port Saver to work well in 8-bit, 16 bit, 32-bit, and 64-bit
systems.
A Write Protect (WP) pin prevents inadvertent writes to
the memory.
Xicor EEPROMs are designed and tested for applica-
tions requiring extended endurance. Inherent data reten-
tion is greater than 100 years.
BLOCK DIAGRAM
System Connection
µP
µC
DSP
ASIC
RISC
Ports
Saved
P0/CS
P1/CLK
P2/DI
P3/DO
A15
WP
Internal Block Diagram
MPS
H.V. GENERATION
TIMING & CONTROL
A0
D7
D0
OE
WE
CE
I/O
OE
WE
COMMAND
DECODE
AND
CONTROL
LOGIC
EEPROM
ARRAY
X
DEC
16K x 8
8K x 8
2K x 8
Y DECODE
DATA REGISTER
7008 FRM F02.1
©
Xicor, Inc. 1994, 1997Patents Pending
7008-1.2 8/26/97 T2/C0/D0 SH
Characteristics subject to change without notice
1
X84161/641/129
PIN CONFIGURATIONS:
Drawings are to the same scale, actual package sizes are shown in inches:
8-LEAD PDIP
8-LEAD SOIC
CE
I/O
WP
V SS
1
2
X84161
3
X84641
4
.230 in.
8
7
6
5
V CC
NC
OE
WE
.190 in.
NC
V
CC
CE
I/O
8-LEAD TSSOP
1
2
3
4
8
7
6
5
OE
WE
WP
VSS
PIN NAMES
.114 in.
X84161
I/O
CE
OE
WE
WP
Data Input/Output
Chip Enable Input
Output Enable Input
Write Enable Input
Write Protect Input
Supply Voltage
Ground
No Connect
7008 FRM T01
.252 in.
20-LEAD TSSOP
14-LEAD SOIC
CE
I/O
NC
NC
NC
WP
V SS
1
2
3
4
5
6
7
.230 in.
X84129
14
13
12
11
10
9
8
V CC
NC
NC
NC
NC
OE
WE
.390 in.
NC
NC
CE
I/O
NC
NC
NC
WP
VSS
NC
1
2
3
4
5
6
7
8
9
10
X84641
20
19
18
17
16
15
14
13
12
11
NC
NC
VCC
NC
NC
NC
NC
OE
WE
NC
V
CC
V
SS
.250 in.
NC
.252 in.
28-LEAD TSSOP
NC
NC
CE
CE
CE
I/O
NC
NC
NC
WP
V
SS
NC
NC
NC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
NC
NC
NC
NC
V
CC
NC
NC .394 in.
NC
NC
OE
WE
NC
NC
NC
PACKAGE
SELECTION GUIDE
84161
8-Lead PDIP
8-Lead SOIC
8-Lead TSSOP
8-Lead PDIP
8-Lead SOIC
20-Lead TSSOP
8-Lead PDIP
14-Lead SOIC
28-Lead TSSOP
7008 FRM T0A
84641
X84129
84129
. 252 in.
7008 FRM F01
PIN DESCRIPTIONS
Chip Enable (CE)
The Chip Enable input must be LOW to enable all read/
write operations. When CE is HIGH, the chip is dese-
lected, the I/O pin is in the high impedance state, and
unless a nonvolatile write operation is underway, the
device is in the standby power mode.
Output Enable (OE)
The Output Enable input must be LOW to enable the out-
put buffer and to read data from the device on the I/O line.
Write Enable (WE)
The Write Enable input must be LOW to write either data
or command sequences to the device.
Data In/Data Out (I/O)
Data and command sequences are serially written to or
serially read from the device through the I/O pin.
Write Protect (WP)
When the Write Protect input is LOW, nonvolatile writes
to the device are disabled. When WP is HIGH, all func-
tions, including nonvolatile writes, operate normally. If a
nonvolatile write cycle is in progress, WP going LOW will
have no effect on the cycle already underway, but will
inhibit any additional nonvolatile write cycles.
2
X84161/641/129
DEVICE OPERATION
The X84161/641/129 are serial EEPROMs designed to
interface directly with most microprocessor buses. Stan-
dard CE, OE, and WE signals control the read and write
operations, and a single l/O line is used to send and
receive data and commands serially.
Data Timing
Data input on the l/O line is latched on the rising edge of
either WE or CE, whichever occurs first. Data output on
the l/O line is active whenever both OE and CE are LOW.
Care should be taken to ensure that WE and OE are
never both LOW while CE is LOW.
Read Sequence
A read sequence consists of sending a 16-bit address
followed by the reading of data serially. The address is
written by issuing 16 separate write cycles (WE and CE
LOW, OE HIGH) to the part without a read cycle between
the write cycles. The address is sent serially, most signifi-
cant bit first, over the I/O line. Note that this sequence is
fully static, with no special timing restrictions, and the pro-
cessor is free to perform other tasks on the bus when-
ever the device CE pin is HIGH. Once the 16 address
bits are sent, a byte of data can be read on the I/O line by
issuing 8 separate read cycles (OE and CE LOW, WE
HIGH). At this point, writing a ‘1’ will terminate the read
sequence and enter the low power standby state, other-
wise the device will await further reads in the sequential
read mode.
Sequential Read
The byte address is automatically incremented to the
next higher address after each byte of data is read. The
data stored in the memory at the next address can be
read sequentially by continuing to issue read cycles.
When the highest address in the array is reached, the
address counter rolls over to address $0000 and reading
may be continued indefinitely.
Reset Sequence
The reset sequence resets the device and sets an inter-
nal write enable latch. A reset sequence can be sent at
any time by performing a read/write “0”/read operation
(see Figs. 1 and 2). This breaks the multiple read or write
cycle sequences that are normally used to read from or
write to the part. The reset sequence can be used at any
time to interrupt or end a sequential read or page load.
As soon as the write “0” cycle is complete, the part is
reset (unless a nonvolatile write cycle is in progress). The
second read cycle in this sequence, and any further read
cycles, will read a HIGH on the l/O pin until a valid read
sequence (which includes the address) is issued. The
reset sequence must be issued at the beginning of both
read and write sequences to be sure the device initiates
these operations properly.
Figure 1. Read Sequence
CE
OE
WE
I/O (IN)
"0"
A15 A14 A13 A12 A11 A10 A9 A8
A7 A6 A5 A4 A3 A2
A1 A0
I/O (OUT)
RESET
WHEN ACCESSING: X84161 ARRAY: A15–A11=0
X84641 ARRAY: A15–A13=0
X84129 ARRAY: A15–A14=0
D7 D6 D5 D4 D3 D2 D1 D0
LOAD ADDRESS
READ DATA
7008 FRM F04.1
3
X84161/641/129
Figure 2: Write Sequence
CE
OE
WE
I/O (IN)
"0"
A15 A14 A13 A12 A11 A10 A9 A8
A7 A6 A5 A4 A3 A2 A1 A0
D7 D6 D5 D4 D3 D2 D1 D0
"1"
"0"
I/O (OUT)
RESET
WHEN ACCESSING:
X84161 ARRAY: A15–A11=0
X84641 ARRAY: A15–A13=0
X84129 ARRAY: A15–A14=0
LOAD ADDRESS
LOAD DATA
START
NONVOLATILE
WRITE
7008 FRM F05.1
Write Sequence
A nonvolatile write sequence consists of sending a reset
sequence, a 16-bit address, up to 32 bytes of data, and
then a special “start nonvolatile write cycle” command
sequence.
The reset sequence is issued first (as described in the
Reset Sequence section) to set an internal write enable
latch. The address is written serially by issuing 16
separate write cycles (WE and CE LOW, OE HIGH) to
the part without any read cycles between the writes. The
address is sent serially, most significant bit first, on the
l/O pin. Up to 32 bytes of data are written by issuing a
multiple of 8 write cycles. Again, no read cycles are
allowed between writes.
The nonvolatile write cycle is initiated by issuing a special
read/write “1”/read sequence. The first read cycle ends
the page load, then the write “1” followed by a read starts
the nonvolatile write cycle. The device recognizes 32-
byte pages (e.g., beginning at addresses XXXXXX00000
for X84161).
When sending data to the part, attempts to exceed the
upper address of the page will result in the address
counter “wrapping-around” to the first address on the
page, where data loading can continue. For this reason,
sending more than 256 consecutive data bits will result in
overwriting previous data.
A nonvolatile write cycle will not start if a partial or incom-
plete write sequence is issued. The internal write enable
latch is reset when the nonvolatile write cycle is com-
pleted and after an invalid write to prevent inadvertent
writes. Note that this sequence is fully static, with no spe-
cial timing restrictions. The processor is free to perform
other tasks on the bus whenever the chip enable pin (CE)
is HIGH.
Nonvolatile Write Status
The status of a nonvolatile write cycle can be determined
at any time by simply reading the state of the l/O pin on
the device. This pin is read when OE and CE are LOW
and WE is HIGH. During a nonvolatile write cycle the l/O
pin is LOW. When the nonvolatile write cycle is complete,
the l/O pin goes HIGH. A reset sequence can also be
issued during a nonvolatile write cycle with the same
result: I/O is LOW as long as a nonvolatile write cycle is
in progress, and l/O is HIGH when the nonvolatile write
cycle is done.
4
X84161/641/129
Low Power Operation
The device enters an idle state, which draws minimal cur-
rent when:
—an illegal sequence is entered. The following are the
more common illegal sequences:
• Read/Write/Write—any time
• Read/Write ‘1’—When writing the address or
writing data.
• Write ‘1’—when reading data
• Read/Read/Write ‘1’—after data is written to
device, but before entering the NV write sequence.
—the device powers-up;
—a nonvolatile write operation completes.
While a sequential read is in progress, the device
remains in an active state. This state draws more current
than the idle state, but not as much as during a read
itself. To go back to the lowest power condition, an invalid
condition is created by writing a ‘1’ after the last bit of a
read operation.
Write Protection
The following circuitry has been included to prevent
inadvertent nonvolatile writes:
—The internal Write Enable latch is reset upon
power-up.
—A reset sequence must be issued to set the internal
write enable latch before starting a write sequence.
—A special “start nonvolatile write” command sequence
is required to start a nonvolatile write cycle.
—The internal Write Enable latch is reset automatically
at the end of a nonvolatile write cycle.
—The internal Write Enable latch is reset and remains
reset as long as the WP pin is LOW, which blocks all
nonvolatile write cycles.
—The internal Write Enable latch resets on an invalid
write operation.
SYMBOL TABLE
WAVEFORM
INPUTS
Must be
steady
May change
from LOW to
HIGH
May change
from HIGH to
LOW
Don’t Care:
Changes
Allowed
N/A
OUTPUTS
Will be
steady
Will change
from LOW to
HIGH
Will change
from HIGH to
LOW
Changing:
State Not
Known
Center Line
is High
Impedance
5
MCU
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