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PDF X4325 Data sheet ( Hoja de datos )
| Número de pieza | X4325 | |
| Descripción | (X4323 / X4325) CPU Supervisor | |
| Fabricantes | Intersil Corporation | |
| Logotipo |  |
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®
Data Sheet
X4323, X4325
32k, 4k x 8 Bit
May 25, 2006
FN8122.1
CPU Supervisor with 32k EEPROM
FEATURES
• Selectable watchdog timer
• Low VCC detection and reset assertion
—Four standard reset threshold voltages
—Adjust low VCC reset threshold voltage using
special programming sequence
—Reset signal valid to VCC = 1V
• Low power CMOS
—<20µA max standby current, watchdog on
—<1µA standby current, watchdog off
—3mA active current
• 32Kbits of EEPROM
—64-byte page write mode
—Self-timed write cycle
—5ms write cycle time (typical)
• Built-in inadvertent write protection
—Power-up/power-down protection circuitry
—Block Lock (1, 2, 4, 8 pages, all, none)
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
— 8 Ld SOICwww.DataSheet4U.com
—8 Ld TSSOP
• Pb-free plus anneal available (RoHS compliant)
BLOCK DIAGRAM
DESCRIPTION
The X4323, X4325 combines four popular functions,
Power-on Reset Control, Watchdog Timer, Supply Volt-
age Supervision, and Serial EEPROM Memory in one
package. This combination lowers system cost,
reduces board space requirements, and increases
reliability.
Applying power to the device activates the power-on
reset circuit which holds RESET/RESET active for a
period of time. This allows the power supply and oscilla-
tor to stabilize before the processor can execute code.
The Watchdog Timer provides an independent protec-
tion mechanism for microcontrollers. When the micro-
controller fails to restart a timer within a selectable time
out interval, the device activates the RESET/RESET
signal. The user selects the interval from three preset
values. Once selected, the interval does not change,
even after cycling the power.
The device’s low VCC detection circuitry protects the
user’s system from low voltage conditions, resetting the
system when VCC falls below the set minimum VCC trip
point. RESET/RESET is asserted until VCC returns to
proper operating level and stabilizes. Four industry
standard VTRIP thresholds are available, however, Inter-
sil’s unique circuits allow the threshold to be repro-
grammed to meet custom requirements or to fine-tune
the threshold for applications requiring higher precision.
WP
SDA
SCL
S0
S1
VCC
Watchdog Transition
Detector
Protect Logic
Data
Register
Command
Decode &
Control
Logic
VCC Threshold
Reset logic
Status
Register
EEPROM Array
VTRIP
+
-
Watchdog
Timer Reset
Reset &
Watchdog
Timebase
Power-on and
Low Voltage
Reset
Generation
RESET (X4323)
RESET (X4325)
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2005-2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
X4323, X4325
PRINCIPLES OF OPERATION
Power-on Reset
Application of power to the X4323, X4325 activates a
Power-on Reset Circuit that pulls the RESET/RESET
pin active. This signal provides several benefits.
– It prevents the system microprocessor from starting
to operate with insufficient voltage.
– It prevents the processor from operating prior to sta-
bilization of the oscillator.
– It allows time for an FPGA to download its configura-
tion prior to initialization of the circuit.
– It prevents communication to the EEPROM, greatly
reducing the likelihood of data corruption on power-up.
When VCC exceeds the device VTRIP threshold value
for 200ms (nominal) the circuit releases
RESET/RESET allowing the system to begin operation.
LOW VOLTAGE MONITORING
During operation, the X4323, X4325 monitors the VCC
level and asserts RESET/RESET if supply voltage
falls below a preset minimum VTRIP. The
RESET/RESET signal prevents the microprocessor
from operating in a power fail or brownout condition.
The RESET/RESET signal remains active until the
voltage drops below 1V. It also remains active until
VCC returns and exceeds VTRIP for 200ms.
WATCHDOG TIMER
The Watchdog Timer circuit monitors the microproces-
sor activity by monitoring the SDA and SCL pins. The
microprocessor must toggle the SDA pin HIGH to
LOW periodically, while SCL is HIGH (this is a start bit)
prior to the expiration of the watchdog time out period to
prevent a RESET/RESET signal. The state of two non-
volatile control bits in the Status Register determine
the watchdog timer period. The microprocessor can
change these watchdog bits, or they may be “locked”
by tying the WP pin HIGH.
EEPROM INADVERTENT WRITE PROTECTION
When RESET/RESET goes active as a result of a low
voltage condition or Watchdog Timer Time Out, any in-
progress communications are terminated. While
RESET/RESET is active, no new communications are
allowed and no nonvolatile write operation can start.
Nonvolatile writes in-progress when RESET/RESET
goes active are allowed to finish.
Additional protection mechanisms are provided with
memory Block Lock and the Write Protect (WP) pin.
These are discussed elsewhere in this document.
VCC THRESHOLD RESET PROCEDURE
The X4323, X4325 is shipped with a standard VCC
threshold (VTRIP) voltage. This value will not change
over normal operating and storage conditions. How-
ever, in applications where the standard VTRIP is not
exactly right, or if higher precision is needed in the
VTRIP value, the X4323, X4325 threshold may be
adjusted. The procedure is described in the following
section, and uses the application of a nonvolatile con-
trol signal.
Figure 1. Set VTRIP Level Sequence (VCC = desired VTRIP values WEL bit set)
WP
SCL
SDA
VP = 12-15V
01234567 01234567
0 1 23 4 56 7
0123456 7
A0h
00h 01h
00h
5 FN8122.1
May 25, 2006
5 Page 
X4323, X4325
Serial Write Operations
BYTE WRITE
For a write operation, the device requires the Slave
Address Byte and a Word Address Byte. This gives the
master access to any one of the words in the array.
After receipt of the Word Address Byte, the device
responds with an acknowledge, and awaits the next
eight bits of data. After receiving the 8-bits of the Data
Byte, the device again responds with an acknowledge.
The master then terminates the transfer by generating a
stop condition, at which time the device begins the inter-
nal write cycle to the nonvolatile memory. During this
internal write cycle, the device inputs are disabled, so the
device will not respond to any requests from the master.
The SDA output is at high impedance. See Figure 8.
Figure 8. Byte Write Sequence
Signals from
the Master
S
t
a
r
t
Slave
Address
Word Address
Byte 1
Word Address
Byte 0
SDA Bus
10 1 0
0
Signals from
the Slave
AA A
CC C
KK K
Data
S
t
o
p
A
C
K
A write to a protected block of memory will suppress the acknowledge bit.
Page Write
The device is capable of a page write operation. It is
initiated in the same manner as the byte write opera-
tion; but instead of terminating the write cycle after the
first data byte is transferred, the master can transmit
an unlimited number of 8-bit bytes. After the receipt of
each byte, the device will respond with an acknowl-
edge, and the address is internally incremented by
one. The page address remains constant. When the
counter reaches the end of the page, it “rolls over” and
goes back to ‘0’ on the same page. This means that
the master can write 64-bytes to the page starting at
any location on that page. If the master begins writing
at location 60, and loads 12-bytes, then the first 4-
bytes are written to locations 60 through 63, and the
last 8-bytes are written to locations 0 through 7. After-
wards, the address counter would point to location 8 of
the page that was just written. If the master supplies
more than 64-bytes of data, then new data over-writes
the previous data, one byte at a time.
Figure 9. Page Write Operation
Signals from
the Master
S
t
a
r
t
Slave
Address
Word Address
Byte 1
Word Address
Byte 0
SDA Bus
10 10
0
Signals from
the Slave
AA
A
CC C
KK
K
Data
(1)
(1 ≤ n ≤ 64)
Data
(n)
A
C
K
S
t
o
p
A
C
K
11 FN8122.1
May 25, 2006
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet X4325.PDF ] | |
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