cards, electronic locks, meters, robotics and telephones,
to name just a few.
ENDURANCE AND DATA RETENTION
The XL9020 is designed for applications requiring up to
100,000 write cycles per bit. It provides 100 years of
secure data retention, with or without power applied.
DEVICE OPERATION
The XL9020 is a clocked serial port compatible E
2
PROM.
It operates on a single power supply ranging from 2.7V to
5.5V and it has an on-chip voltage generator to provide
the high voltage needed during a programming operation.
Input data is latched on the rising edge of the clock(SK),
and data is output on the falling edge of the clock.
Data is grouped in 8-bit bytes. The beginning 8 bits specify
the mode, the next 8 bits specify the address, and subse-
quent 16 bits specify the I/O data. Each instruction sent to
the device includes a 4 bit start sequence, 1010, a 4 bit
opcode and an 8 bit address including a dummy bit at the
end. For a WRITE operation, a 16 bit data field is required
following the 8 bit address field. The device requires an
active LOW
CS
in order to be selected. Each instruction
must be preceded by a HIGH-to-LOW transition of
CS
before the 4 bit start sequence is given. Prior to the 4 bit
start sequence (1010), inputs of all other logical sequence
are ignored.
During the self-timed internal programming cycle that
accompanies a write, the
SK
clock is deactivated. It is
needed only when instructions or data are being passed
to or from the memory.
Any of the four modes (read, write, write enable, write
disable) may be specified. The write time is set by internal
timer, and determination of whether a write operation is in
progress or not can be made from the status of the
READY/BUSY pin.
Read (READ)
The read instruction is the only instruction that outputs
serial data on the DO pin. After the read instruction and
address have been decoded, data is transferred from the
selected memory register into the output register. The
output on DO changes during the HIGH to LOW transition
of
SK.
Write (WRITE)
After a write instruction and its address have been de-
coded, the device expects 16 bits of data. These are to be
transferred into the specific memory register which has
previously been automatically erased. After the last data
bit has been clocked into DI on the 32nd clock edge, the
D0018 5/96
DVPTD 6931-05
2
XL9020
self-timed internal programming cycle is initiated. The
write cycle status can be monitored by observing the
READY/BUSY pin. It will output the
BUSY
status (LOW)
one t
SV
after the rising edge of the 32nd clock (the last
data bit) and will stay LOW until the WRITE cycle is
complete. It will then output a HIGH status until the next
WRITE cycle.
CS
must be held HIGH for the minimum of
t
CS
before the next instruction is entered.
Another way to get READY/BUSY status is from the DO
pin. During a WRITE cycle, asserting a LOW on the
CS
pin will cause the DO pin to output the READY/BUSY
status. It is necessary for
SK
to be brought into a LOW
state 500ns prior to
CS
going LOW. Asserting a HIGH on
CS
will put the DO pin in a high impedance state again.
After the WRITE cycle is completed, the DO pin will output
HIGH when the device is deselected. The first rising edge
of the DI pin will reset DO back into the high impedance
state.
Write Control (WC PIN)
WC
The
WC
pin provides hardware write control. When
WC
pin is low, the chip is enabled to execute WRITE functions.
When
WC
pin is high, all WRITE functions are locked out.
The device shows ready status on the R/B pin and on the
DO pin, if
CS
and
SK
are low. In addition, if
WC
pin
changes state during the write cycle, the write operation
will be aborted not guaranteeing the data. The
WC
pin
does not have any effect on the READ, EWEN and EWDS
operations.
Write Enable/Disable
When the XL9020 is powered up, it comes up in the write
disabled state. In order to be programmable, it must
receive an enable instruction. The device remains pro-
grammable until a disable instruction is entered, or until it
is powered down. The disable instruction provides protec-
tion against inadvertent writes. Read operation is not
affected by this command.
INSTRUCTION SET
Instruction
READ
WRITE
Erase/Write Enable (EWEN)
Erase/Write Disable (EWDS)
Start
Bits
1010
1010
1010
1010
OP
Code
1000
0100
0011
0000
Address
Data
(A
0
-A
6
) 0
(A
0
-A
6
) 0
XXXXXXXX
XXXXXXXX
D0018 PGM T01.1
Input
D
0
-D
15
3
D0018 5/96
DVPTD 6931-05
XL9020
ABSOLUTE MAXIMUM RATINGS
Temperature under bias ..................................................................................................................... -40°C to +85°C
Storage Temperature. ...................................................................................................................... -65°C to +150°C
Lead Soldering Temperature (less than 10 seconds) ...................................................................................... 300°C
Supply Voltage ......................................................................................................................................... -0.3 to 7.0V
Voltage on Any Pin. ........................................................................................................................ .-0.3 to Vcc +0.3V
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