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PDF X4645 Data sheet ( Hoja de datos )
| Número de pieza | X4645 | |
| Descripción | (X4643 / X4645) CPU Supervisor | |
| Fabricantes | Xicor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de X4645 (archivo pdf) en la parte inferior de esta página. Total 22 Páginas | ||
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Preliminary Information
64K X4643/5
CPU Supervisor with 64K EEPROM
8K x 8 Bit
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
• 64Kbits 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
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
—8-lead SOIC
—8-lead TSSOP
DESCRIPTION
The X4643/5 combines four popular functions, Power-on
Reset Control, Watchdog Timer, Supply Voltage
Supervision, and Serial EEPROM Memory in one
package. This combination lowers system cost,
reduces board space requirements, and increases reli-
ability.
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 protection
mechanism for microcontrollers. When the microcon-
troller 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
BLOCK DIAGRAM
WP
SDA
SCL
S0
S1
Watchdog Transition
Detector
Data
Register
Command
Decode &
Control
Logic
VCC Threshold
Reset Logic
Protect Logic
Status
Register
EEPROM Array
VCC
VTRIP
+
-
Watchdog
Timer Reset
Reset &
Watchdog
Timebase
Power on and
Low Voltage
Reset
Generation
RESET (X4643/5)
RESET (X4645)
REV 1.26 4/30/02
www.xicor.com
Characteristics subject to change without notice. 1 of 22
Free Datasheet http://www.datasheet4u.com/
1 page  
X4643/5 – Preliminary Information
Figure 4. VTRIP Programming Sequence
VTRIP Programming
Execute
Reset VTRIP
Sequence
Set VCC = VCC Applied =
Desired VTRIP
New VCC Applied =
Old VCC Applied + Error
Execute
Set VTRIP
Sequence
Apply 5V to VCC
Decrement VCC
(VCC = VCC - 50mV)
New VCC Applied =
Old VCC Applied - Error
Execute
Reset VTRIP
Sequence
NO RESET pin
goes active?
YES
Error ≤ –Emax
Emax = Maximum Allowed VTRIP Error
Measured VTRIP -
Desired VTRIP
Error ≥ Emax
–Emax < Error < Emax
DONE
Control Register
The Control Register provides the user a mechanism
for changing the Block Lock and Watchdog Timer set-
tings. The Block Lock and Watchdog Timer bits are
nonvolatile and do not change when power is removed.
The Control Register is accessed at address FFFFh. It
can only be modified by performing a byte write opera-
tion directly to the address of the register and only one
data byte is allowed for each register write operation.
Prior to writing to the Control Register, the WEL and
RWEL bits must be set using a two step process, with
the whole sequence requiring 3 steps. See "Writing to
the Control Register" below.
The user must issue a stop after sending this byte to the
register to initiate the nonvolatile cycle that stores WD1,
and WD0. The X4643/5 will not acknowledge any data
bytes written after the first byte is entered.
The state of the Control Register can be read at any
time by performing a random read at address FFFFh.
Only one byte is read by each register read operation.
REV 1.26 4/30/02
www.xicor.com
Characteristics subject to change without notice. 5 of 22
Free Datasheet http://www.datasheet4u.com/
5 Page 
X4643/5 – Preliminary Information
Serial Read Operations
Read operations are initiated in the same manner as
write operations with the exception that the R/W bit of
the Slave Address Byte is set to one. There are three
basic read operations: Current Address Reads, Ran-
dom Reads, and Sequential Reads.
Current Address Read
Internally the device contains an address counter that
maintains the address of the last word read incre-
mented by one. Therefore, if the last read was to
address n, the next read operation would access data
from address n+1. On power up, the address of the
address counter is undefined, requiring a read or write
operation for initialization.
Figure 12. Current Address Read Sequence
Upon receipt of the Slave Address Byte with the R/W
bit set to one, the device issues an acknowledge and
then transmits the eight bits of the Data Byte. The mas-
ter terminates the read operation when it does not
respond with an acknowledge during the ninth clock
and then issues a stop condition. Refer to Figure 12 for
the address, acknowledge, and data transfer
sequence.
It should be noted that the ninth clock cycle of the read
operation is not a “don’t care.” To terminate a read
operation, the master must either issue a stop condi-
tion during the ninth cycle or hold SDA HIGH during
the ninth clock cycle and then issue a stop condition.
Signals from
the Master
SDA Bus
Signals from
the Slave
S
t
a
r
t
Slave
Address
1 010
1
A
C
K
Data
S
t
o
p
Random Read
Random read operation allows the master to access
any memory location in the array. Prior to issuing the
Slave Address Byte with the R/W bit set to one, the
master must first perform a “dummy” write operation.
The master issues the start condition and the Slave
Address Byte, receives an acknowledge, then issues
the Word Address Bytes. After acknowledging receipts
of the Word Address Bytes, the master immediately
issues another start condition and the Slave Address
Byte with the R/W bit set to one. This is followed by an
acknowledge from the device and then by the eight bit
word. The master terminates the read operation by not
responding with an acknowledge and then issuing a
stop condition. Refer to Figure 13 for the address,
acknowledge, and data transfer sequence.
Figure 13. Random Address Read Sequence
Signals from
the Master
SDA Bus
Signals from
the Slave
S
t
a Slave
r Address
t
Word Address
Byte 1
Word Address
Byte 0
S
t
a
r
t
101 0
0
AAA
CCC
KKK
Slave
Address
1
A
C
K
Data
S
t
o
p
REV 1.26 4/30/02
www.xicor.com
Characteristics subject to change without notice. 11 of 22
Free Datasheet http://www.datasheet4u.com/
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet X4645.PDF ] | |
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