SUMMIT
MICROELECTRONICS, Inc.
S24042/S24043
3 and 5 Volt Systems
Precision RESET Controller and 4K I
2
C Memory
With Both RESET and
RESET
Outputs
FEATURES
• Precision Supply Voltage Monitor
— Dual reset outputs for complex
microcontroller systems
— Integrated memory write lockout
• Guaranteed RESET (RESET#) assertion
to V
CC
=1V
• Power-Fail Accuracy Guaranteed
• No External Components
• 3 and 5 Volt system versions
• Low Power CMOS
— Active current less than 3mA
— Standby current less than 25µA
• Memory Internally Organized 512 X 8
— Two Wire Serial Interface (I
2
C™)
– Bidirectional data transfer protocol
– Standard 100KHz and Fast 400KHz
•
•
High Reliability
— Endurance: 100,000 erase/write cycles
— Data retention: 100 years
8-Pin PDIP or SOIC Packages
OVERVIEW
The S24042 and S24043 are power supervisory devices
with 4,096 bits of serial E
2
PROM. They are fabricated
using SUMMIT’s advanced CMOS E
2
PROM technology
and are suitable for both 3 and 5 volt systems.
The memory is internally organized as 512 x 8. It features
the I
2
C serial interface and software protocol allowing
operation on a simple two-wire bus.
The S24042 provides a precision V
CC
sense circuit and
two open drain outputs: one (RESET) drives high and the
other (RESET#) drives low whenever V
CC
falls below
V
TRIP
. The S24043 is identical to the S24042 with the
exception being RESET is not bonded out on pin 7.
BLOCK DIAGRAM
VCC
22
5kHz
OSCILLATOR
RESET
PULSE
GENERATOR
2
RESET#
+
–
VTRIP
RESET
CONTROL
7
RESET
1.26V
SCL
SDA
6
5
MODE
DECODE
ADDRESS
DECODER
WRITE
CONTROL
DATA I/O
E2PROM
MEMORY
ARRAY
4
2011 T-BD 1.0
GND
SUMMIT MICROELECTRONICS, Inc.
•
300 Orchard City Drive, Suite 131
•
Campbell, CA 95008
•
Telephone 408-378-6461
•
Fax 408-378-6586
•
www.summitmicro.com
© SUMMIT MICROELECTRONICS, Inc. 2000
2011 2.0 5/2/00
Characteristics subject to change without notice
1
S24042/S24043
PIN CONFIGURATIONS
RESET #- RESET#
is an active low open drain output.
It is driven low whenever V
CC
is below V
TRIP
.
It
is also
an input and can be used to debounce a switch input or
perform signal conditioning. The pin has an internal pull-
up and should be left unconnected if the signal is not used
in the system. However, when the pin is tied to a system
RESET# line an external pull-up resistor should be
employed.
RESET
- RESET is an active high open drain output. It is
driven high whenever V
CC
is below V
TRIP
. RESET is also
an input and can be used to debounce a switch input or
perform signal conditioning. The RESET pin does have
an internal pull-down and should be left unconnected if
the signal is not used in the system. However, when the
pin is tied to a system reset line an external pull-down
resistor should be employed.
NC
1
RESET#
2
NC
3
V
SS
4
S24042
8
V
CC
7
RESET
6
SCL
5
SDA
NC
1
S24043
RESET#
2
NC
3
V
SS
4
8
V
CC
7
NC
6
SCL
5
SDA
2011 PCon 2.0
ENDURANCE AND DATA RETENTION
The S24042/43 is designed for applications requiring
100,000 erase/write cycles and unlimited read cycles. It
provides 100 years of secure data retention, with or
without power applied, after the execution of 100,000
erase/write cycles.
APPLICATIONS
Reset Controller Description
The S24042/43 provides a precision RESET controller
that ensures correct system operation during brown-out
and power-up/-down conditions. It is configured with two
open drain RESET outputs; pin 7 is an active high output
and pin 2 is an active low output.
During power-up, the RESET outputs remain active until
V
CC
reaches the V
TRIP
threshold and will continue driving
the outputs for approximately 200ms after reaching
V
TRIP
. The RESET outputs will be valid so long as V
CC
is
> 1.0V. During power-down, the RESET outputs will
begin driving active when V
CC
falls below V
TRIP
.
The RESET pins are I/Os; therefore, the S24042/43 can
act as a signal conditioning circuit for an externally
applied reset. The inputs are edge triggered; that is, the
RESET input will initiate a reset timeout after detecting a
low to high transition and the RESET# input will initiate a
reset timeout after detecting a high to low transition. Refer
to the applications Information section for more details on
device operation as a reset conditioning circuit.
PIN NAMES
SDA
SCL
RESET &
RESET#
V
SS
V
CC
NC
PIN DESCRIPTIONS
Serial Clock (SCL)
- The SCL input is used to clock data
into and out of the device. In the WRITE mode, data must
remain stable while SCL is HIGH. In the READ mode, data
is clocked out on the falling edge of SCL.
Serial Data (SDA)
- The SDA pin is a bidirectional pin
used to transfer data into and out of the device. Data may
change only when SCL is LOW, except START and STOP
conditions. It is an open-drain output and may be wire-
ORed with any number of open-drain or open-collector
outputs.
No Connects (NC)
the no connect pins may be left
floating or tied to ground. They cannot be tied high.
Serial Data I/O
Serial Clock Input
Reset Output
Ground
Supply Voltage
No Connect
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SUMMIT MICROELECTRONICS, Inc.
2
S24042/S24043
VCC = 3.0 0r 5.0
S24042
1
Vcc
2
RESET#
3
SCL
4
Vss
SDA
5
SDA
RESET
6
SCL
7
RESET
8
8051 Type MCU
I
2
C
Peripheral
RESET#
SCL
SDA
2011 T fig01 2.0
FIGURE 1. TYPICAL SYSTEM CONFIGURATION FOR DUAL RESET
SCL
START
Condition
STOP
Condition
SDA In
2011 ILL5 1.0
FIGURE 2. START AND STOP CONDITIONS
2011 2.0 5/2/00
SUMMIT MICROELECTRONICS, Inc.
3
S24042/S24043
SCL from
Master
Data Output
from
Transmitter
Data Output
from
Receiver
Start
Condition
1
8
9
t
AA
t
AA
ACKnowledge
2011 ILL6 1.0
FIGURE 3. ACKNOWLEDGE RESPONSE FROM RECEIVER
CHARACTERISTICS OF THE I
2
C BUS
General Description
The I
2
C bus was designed for two-way, two-line serial
communication between different integrated circuits. The
two lines are: a serial data line (SDA), and a serial clock
line (SCL). The SDA line must be connected to a positive
supply by a pull-up resistor, located somewhere on the
bus (See Figure 1). Data transfer between devices may
be initiated with a START condition only when SCL and
SDA are HIGH (bus is not busy).
Input Data Protocol
One data bit is transferred during each clock pulse. The
data on the SDA line must remain stable during clock
HIGH time, because changes on the data line while SCL
is HIGH will be interpreted as start or stop condition, refer
to Figure 10.
START and STOP Conditions
When both the data and clock lines are HIGH, the bus is
said to be not busy. A HIGH-to-LOW transition on the data
line, while the clock is HIGH, is defined as the “START”
condition. A LOW-to-HIGH transition on the data line,
while the clock is HIGH, is defined as the “STOP” condi-
tion (See Figure 2).
DEVICE OPERATION
The S24042/43 is a 4,096-bit serial E
2
PROM. The device
supports the I
2
C bidirectional data transmission protocol.
The protocol defines any device that sends data onto the
bus as a “transmitter” and any device which receives data
as a “receiver.” The device controlling data transmission
is called the “master” and the controlled device is called
the “slave.” In all cases, the S24042/43 will be a “slave”
device, since it never initiates any data transfers.
Acknowledge (ACK)
Acknowledge is a software convention used to indicate
successful data transfers. The transmitting device, either
the master or the slave, will release the bus after transmit-
ting eight bits. During the ninth clock cycle, the receiver
will pull the SDA line LOW to ACKnowledge that it re-
ceived the eight bits of data (See Figure 3).
The S24042/43 will respond with an ACKnowledge after
recognition of a START condition and its slave address
byte. If both the device and a write operation are selected,
the S24042/43 will respond with an ACKnowledge after
the receipt of each subsequent 8-bit word.
In the READ mode, the S24042/43 transmits eight bits of
data, then releases the SDA line, and monitors the line for
an ACKnowledge signal. If an ACKnowledge is detected,
and no STOP condition is generated by the master, the
S24042/43 will continue to transmit data. If an
ACKnowledge is not detected, the S24042/43 will termi-
nate further data transmissions and awaits a STOP condi-
tion before returning to the standby power mode.
Device Addressing
Following a start condition the master must output the
address of the slave it is accessing. The most significant
four bits of the slave address are the device type identifier
(see figure 4). For the S24042/43 this is fixed as 1010[B].
The next two bits are don’t care. The next bit is the high
order address bit A8.
DEVICE
IDENTIFIER
DON’T CARE
1
0
1
0
X
X
A
8
R/W
2011 ILL7 1.1
FIGURE 4. SLAVE ADDRESS BYTE
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SUMMIT MICROELECTRONICS, Inc.
4
S24042/S24043
Read/Write Bit
The last bit of the data stream defines the operation to be
performed. When set to “1,” a read operation is selected;
when set to “0,” a write operation is selected.
WRITE OPERATIONS
The S24042/43 allows two types of write operations: byte
write and page write. The byte write operation writes a
single byte during the nonvolatile write period (t
WR
). The
page write operation allows up to 16 bytes in the same
page to be written during t
WR
.
Byte WRITE
Upon receipt of the slave address and word address, the
S24042/43 responds with an ACKnowledge. After receiv-
ing the next byte of data, it again responds with an
ACKnowledge. The master then terminates the transfer
by generating a STOP condition, at which time the
S24042/43 begins the internal write cycle.
While the internal write cycle is in progress, the S24042/
43 inputs are disabled, and the device will not respond to
any requests from the master. Refer to Figure 5 for the
address, ACKnowledge and data transfer sequence.
Page WRITE
The S24042/43 is capable of a 16-byte page write opera-
tion. It is initiated in the same manner as the byte-write
operation, but instead of terminating the write cycle after
the first data word, the master can transmit up to 15 more
bytes of data. After the receipt of each byte, the S24042/
43 will respond with an ACKnowledge.
The S24042/43 automatically increments the address for
subsequent data words. After the receipt of each word,
the low order address bits are internally incremented by
one. The high order five bits of the address byte remain
constant. Should the master transmit more than 16 bytes,
prior to generating the STOP condition, the address
counter will “roll over,” and the previously written data will
be overwritten. As with the byte-write operation, all inputs
are disabled during the internal write cycle. Refer to
Figure 5 for the address, ACKnowledge and data transfer
sequence.
Acknowledges Transmitted from
24042/43 to Master Receiver
If single byte-write only,
Stop bit issued here.
Acknowledges Transmitted from
24042/43 to Master Receiver
SDA
Bus
Activity
1010
X X A R
8 W
A
C
Word Address
K
A A A A A A A A
7 6 5 4 3 2 1 0
A
C
K
Data Byte n
A
C
K
A
Data Byte n+1
C
K
D D D D D D D D
7 6 5 4 3 2 1 0
Data Byte n+15
C
K
D D D D D D D D
7 6 5 4 3 2 1 0
A
A
8
0
D D D D D D D D
7 6 5 4 3 2 1 0
S
T Device
Type
A
R Address
Read/Write
T
0= Write
S
T
O
P
Slave Address
Master Sends Read
Request to Slave
Master Writes Word
Address to Slave
Master Writes
Data to Slave
Master Writes
Data to Slave
Master Writes
Data to Slave
Master Transmitter
to
Slave Receiver
Master Transmitter
to
Slave Receiver
Master Transmitter
to
Slave Receiver
Master Transmitter
to
Slave Receiver
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
2011 ILL8 1.0
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
Shading Denotes
24042/43
SDA Output Active
FIGURE 5. PAGE/BYTE WRITE MODE
2011 2.0 5/2/00
SUMMIT MICROELECTRONICS, Inc.
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