ETC SMS2916SB

SUMMIT
SMS2916
Preliminary
MICROELECTRONICS, Inc.
3 and 5 Volt Systems
Precision Voltage Supervisory Circuit
With Watchdog Timer and 16K I2C Memory
FEATURES
• Precision Voltage Monitor
– Automatic VCC Supply Monitor
- Complementary reset outputs for complex
microcontroller systems
- Integrated memory write lockout function
- No external components required
• Watchdog Timer
– Nominal 1.6 second Timeout
• Memory Internally Organized 2K X 8
– Two Wire Serial Interface (I2C™)
• High Reliability
– Endurance: 1,000,000 erase/write cycles
– Data retention: 100 years
• 8-Pin PDIP or SOIC Packages
OVERVIEW
The SMS2916 is a power supervisory circuit that monitors
VCC (either in a 5V system or 3V system) and will generate
complementary reset outputs. The reset pins also act as
I/Os and may be used for signal conditioning. The
SMS2916 also has an on-board watchdog timer that has
a nominal time out period of 1.6 seconds.
The SMS2916 integrates a 16K-bit nonvolatile serial
memory. It features the industry standard I2C serial
interface allowing quick implementation in an end-users’
system.
BLOCK DIAGRAM
VCC 8
2
RESET
RESET
PULSE
GENERATOR
5KHz
Oscillator
VCC
+
VTRIP
RESET
CONTROL
GND 4
7
RESET
1.26V
WATCHDOG
TIMER
SCL
6
SDA
5
WDI
1
SUMMIT MICROELECTRONICS, Inc.
EEPROM
MEMORY
ARRAY
2028 ILL2.1
•
300 Orchard City Drive, Suite 131
© SUMMIT MICROELECTRONICS, Inc. 1998
2028-02 4/24/98
•
Campbell, CA 95008
•
Telephone 408-378-6461
•
Fax 408-378-6586
•
www.summitmicro.com
Characteristics subject to change without notice
1
SMS2916
Preliminary
PIN NAMES
PIN CONFIGURATIONS
WDI
1
8
VCC
RESET
2
7
RESET
NC
3
6
SCL
GND
4
5
SDA
2028 ILL1.2
Symbol
Pin
Description
WDI
1
Watchdog Input /a high to
low transition will clear the
watchdog timer
RESET
2
Active Low RESET Input/Output
NC
3
No Connect, tie to ground
or leave open
GND
4
Analog and Digital Ground
SDA
5
Serial Memory Input/
Output data line
SCL
6
Serial Memory clock input
RESET
7
Active High RESET Input/
Output
VCC
8
Supply Voltage
2028 PGM T1.1
VCC = 3.0 0r 5.0
PB_RST
ALE
SMS2916
WDI
8051 Type MCU
Vcc
RESET RESET
RST
NC
SCL
SCL (P0.0)
GND
SDA
SDA (P0.1
I 2C
Peripheral
RESET
SCL
2028 ILL3.1
SDA
FIGURE 1. TYPICAL APPLICATION USING DUAL RESET FUNCTION AND WATCHDOG TIMER
2028-02 4/24/98
2
SMS2916
Preliminary
Decoder
+5VDC
RST
SMS 2916
Z80
WDI Vcc
RESET
RESET
SCL
I/O
GND SDA
I/O
NC
2028 ILL4.1
FIGURE 2. TYPICAL APPLICATION CONFIGURATION USING SYSTEM DECODE LOGIC TO RESET WDI
CAPACITANCE
TA = 25°C, f = 100KHz
Symbol
CIN
LOUT
Parameter
Max
Units
Input Capacitance
5
pF
Output Capacitance
8
pF
2028 PGM T2..0
tR
tH IGH
tLOW
tSU:STO
tF
SCL
tSU:SDA tHD:SDA
tSU:DAT
tHD:DAT
tBUF
SDA In
tDH
tAA
SDA Out
2028 ILL5.0
FIGURE 3. BUS TIMING
2028-02 4/24/98
3
SMS2916
Preliminary
ABSOLUTE MAXIMUM RATINGS
Temperature Under Bias
............................................................................................................................... -40°C to +85°C
Storage Temperature
..................................................................................................................................... -65°C to +125°C
Soldering Temperature (less than 10 seconds) ................................................................................................................... 300°C
Supply Voltage ............................................................................................................................................................. 0 to 6.5V
Voltage on Any Pin ....................................................................................................................................... -0.3V to VCC+0.3V
ESD Voltage (JEDEC method) .......................................................................................................................................... 2,000V
NOTE: These are STRESS ratings only. Appropriate conditions for operating these devices are given elsewhere in this specification. Stresses
beyond those listed here may permanently damage the part. Prolonged exposure to maximum ratings may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
Temperature
Commercial
Min
0°C
Max
+70°C
Industrial
-40°C
+85°C
2028 PGM T3.0
DC ELECTRICAL CHARACTERISTICS (over recommended operating conditions unless otherwise specified)
Symbol
Parameter
Supply Current (CMOS)
ICC
ISB
Standby Current (CMOS)
Conditions
Min
Max
Units
3
mA
SCL = CMOS Levels @ 100KHz
SDA = Open
All other inputs = GND or VCC
VCC =5.5V
VCC =3.3V
2
mA
SCL = SDA = VCC
All other inputs = GND
VCC =5.5V
50
µA
VCC =3.3V
25
µA
ILI
Input Leakage
VIN = 0 To VCC
10
µA
ILO
Output Leakage
VOUT = 0 To VCC
10
µA
VIL
Input Low Voltage
S0, S1, S2, SCL, SDA, RESET
0.3xVCC
V
VIH
Input High Voltage
S0, S1, S2, SCL, SDA, RESET
VOL
Output Low Voltage
IOL = 3mA SDA
0.7xVCC
V
0.4
V
2028 PGM T4.0
AC ELECTRICAL CHARACTERISTICS
(over recommended operating conditions unless otherwise specified)
Symbol
Parameter
Conditions
2.7V to 4.5V
4.5V to 5.5V
Min
Max
Min
0
100
Max
Units
400
KHz
fSCL
SCL Clock Frequency
tLOW
Clock Low Period
4.7
1.3
µs
tHIGH
Clock High Period
4.0
0.6
µs
tBUF
Bus Free Time
4.7
1.3
µs
tSU:STA
Start Condition Setup Time
4.7
0.6
µs
tHD:STA
Start Condition Hold Time
4.0
0.6
µs
tSU:STO
Stop Condition Setup Time
4.7
0.6
µs
tAA
Clock to Output
SCL Low to SDA Data Out Valid
0.3
tDH
Data Out Hold Time
SCL Low to SDA Data Out Change
0.3
tR
SCL and SDA Rise Time
1000
300
ns
tF
SCL and SDA Fall Time
300
300
ns
tSU:DAT
Data In Setup Time
250
100
ns
tHD:DAT
Data In Hold Time
0
0
ns
TI
Noise Spike Width
@ SCL, SDA Inputs
tWR
Write Cycle Time
Before New Transmission
Noise Suppression Time Constant
3.5
0.2
0.9
µs
µs
0.2
100
100
ns
10
10
ms
2028 PGM T5.0
2028-02 4/24/98
4
SMS2916
Preliminary
tGLITCH
VTRIP
VRVALID
tRPD
VCC
tPURST
tPURST
RESET
tRPD
RESET
2028 ILL6.0
FIGURE 4. RESET OUTPUT TIMING
RESET CIRCUIT AC and DC ELECTRICAL CHARACTERISTICS
TA = -40°C to +85°C
SMS2916-2.7
Symbol
Parameter
SMS2916–A
SMS2916–B
Min
Max
Min
Max
Min
Max
Unit
VTRIP
Reset Trip Point
2.55
2.7
4.25
4.5
4.5
4.75
V
tPURST
Power-Up Reset Timeout
130
270
130
270
130
270
ms
tRPD
VTRIP to RESET Output Delay
5
µs
VRVALID
RESET Output Valid
tGLITCH
Glitch Reject Pulse Width
30
30
30
ns
VOLRS
RESET Output Low Voltage IOL= 1mA
0.4
0.4
0.4
V
VOHRS
RESET Output High Voltage IOH = 800 µA
5
1
VCC-.75
5
1
VCC-.75
1
VCC-.75
V
V
2028 PGM T6.0
2028-02 4/24/98
5
SMS2916
Preliminary
PIN DESCRIPTIONS
The RESET pins are I/Os; therefore, the SMS2916 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.
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 wireORed with any number of open-drain or open-collector
outputs.
WATCHDOG TIMER OPERATION
The SMS2916 has a watchdog timer with a nominal
timeout period of 1.6 seconds. Whenever the watchdog
times out it will generate a reset output on both RESET
and RESET. There are two methods of clearing the
watchdog timer; the first is through the use of software,
and the second is by strobing the WDI input pin.
RESET - RESET is an active low output. Whenever VCC
is below VTRIP the SMS2916 will drive the RESET pin to
ground. The RESET pin is an I/O and can be used as a
reset input. Refer to Figure 1 as an example use of this pin
as a push button switch debounce circuit. It should be
noted this is an open drain output and an external pull-up
resistor tied to VCC is needed for proper operation.
Software Method
The watchdog timer will clear to t0 whenever the
SMS2916 issues an ACKnowledge. Therefore, the host
system will need to issue a start condition, followed by a
valid address and command. It can be a normal command as in the sequence of reading or writing to the
memory, or it can be a dummy command issued solely for
the purpose of resetting the watchdog timer. Refer to
Figure 12 for detailed sequence of operations.
RESET — RESET is an active high output. Whenever
VCC is below VTRIP the SMS2916 will drive the RESET pin
to the VCC rail. The RESET pin is an I/O and can be used
as a reset input. It should be noted this is an open drain
output and an external pull-down resistor tied to ground is
needed for proper operation.
WDI - The WDI input is used as a hardware method of
clearing the watchdog timer. A high to low transition on
this pin will clear the watchdog timer. If a transition is not
detected within 1.6 seconds the watchdog will time out
and force the reset outputs active.
The watchdog timer will be held in the cleared state during
power-on while VCC is less than VTRIP. Once VCC exceeds VTRIP the watchdog will continue to be held in a
cleared state for the duration of tPURST. After tPURST, the
timer will be released and begin counting.
ENDURANCE AND DATA RETENTION
If either reset input is asserted the watchdog timer will be
cleared and remain in the reset condition until either
tPURST has expired or the reset input is released, whichever is longer.
The SMS2916 is designed for applications requiring
1,000,000 erase/write cycles and unlimited read cycles. It
provides 100 years of secure data retention, with or
without power applied, after the execution of 1,000,000
erase/write cycles.
If the watchdog times out and no action is taken by the
host the SMS2916 will drive the reset outputs active for
the duration of tPURST at which point it will release the
outputs and clear the watchdog timer again and release
it to begin a new count. Refer to Figure 13 for detailed
sequence of operations.
Reset Controller Description
The SMS2916 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.
Hardware Method
A high to low transition on WDI will clear the watchdog
timer. If a transition is not detected within 1.6 seconds the
watchdog will time out and force the reset outputs active.
During power-up, the RESET outputs remain active until
VCC reaches the VTRIP threshold and will continue driving
the outputs for approximately 200ms after reaching VTRIP.
The RESET outputs will be valid so long as VCC is > 1.0V.
During power-down, the RESET outputs will begin driving
active when VCC falls below VTRIP.
2028-02 4/24/98
6
SMS2916
Preliminary
SCL from
Master
Data Output
from
Transmitter
1
9
8
Start
Condition
tAA
Data Output
from
Receiver
ACKnowledge
tAA
2028 ILL7.0
FIGURE 5. ACKNOWLEDGE RESPONSE FROM RECEIVER
CHARACTERISTICS OF THE I2C BUS
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 transmitting eight bits. During the ninth clock cycle, the receiver
will pull the SDA line LOW to ACKnowledge that it received the eight bits of data (See Figure 5).
General Description
The I2C 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).
The SMS2916 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 SMS2916 will respond with an ACKnowledge after the
receipt of each subsequent 8-bit word.
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.
In the READ mode, the SMS2916 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
SMS2916 will continue to transmit data. If an
ACKnowledge is not detected, the SMS2916 will terminate
further data transmissions and awaits a STOP condition
before returning to the standby power mode.
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” condition .
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 6). For the SMS2916 this is fixed as 1010[B].
DEVICE OPERATION
The SMS2916 is a 16K-bit serial E2PROM. The device
supports the I2C 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 SMS2916 will be a “slave”
device, since it never initiates any data transfers.
DEVICE
IDENTIFIER
1
0
1
0
A
10
A
9
A
8
R/W
2028 ILL8.0
FIGURE 6. SLAVE ADDRESS BYTE
2028-02 4/24/98
7
SMS2916
Preliminary
The next three bits are the high order address bit A8.
While the internal write cycle is in progress, the SMS2916
inputs are disabled, and the device will not respond to any
requests from the master. Refer to Figure 7 for the
address, ACKnowledge and data transfer sequence.
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.
Page WRITE
The SMS2916 is capable of a 16-byte page write operation. 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 SMS2916
will respond with an ACKnowledge.
WRITE OPERATIONS
The SMS2916 allows two types of write operations: byte
write and page write. The byte write operation writes a
single byte during the nonvolatile write period (tWR). The
page write operation allows up to 16 bytes in the same
page to be written during tWR.
The SMS2916 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 7 for the address, ACKnowledge and data transfer
sequence.
Byte WRITE
Upon receipt of both the slave address and word address,
the SMS2916 responds with an ACKnowledge for each.
After receiving 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
SMS2916 begins the internal write cycle.
If single byte-write only,
Stop bit issued here.
Acknowledges Transmitted from
SMS2916 to Master Receiver
SDA
Bus
Activity
A A X R
10 9
W
1010
A A
X
10 9
0
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
D D D D D D D D
7 6 5 4 3 2 1 0
A
C
K
Acknowledges Transmitted from
SMS2916 to Master Receiver
A
A
Data Byte n+1 C
Data Byte n+15 C
K
K
D D D D D D D D
7 6 5 4 3 2 1 0
D D D D D D D D
7 6 5 4 3 2 1 0
S
T
O
P
S
T Device
Type
A
R Address Read/Write
T
0= Write
Slave Address
Master Sends Read
Request to Slave
Master Transmitter
to
Slave Receiver
Master Writes Word
Address to Slave
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
Master Writes
Data to Slave
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
Master Writes
Data to Slave
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
Master Writes
Data to Slave
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
2028 ILL9.0
Shading Denotes
SMS2916
SDA Output Active
FIGURE 7. PAGE/BYTE WRITE MODE
2028-02 4/24/98
8
SMS2916
Preliminary
Acknowledge Polling
When the SMS2916 is performing an internal WRITE
operation, it will ignore any new START conditions. Since
the device will only return an acknowledge after it accepts
the START, the part can be continuously queried until an
acknowledge is issued, indicating that the internal WRITE
cycle is complete.
READ OPERATIONS
Read operations are initiated with the R/W bit of the
identification field set to “1.” There are four different read
options:
1.
2.
3.
4.
To poll the device, give it a START condition, followed by
a slave address for a WRITE operation (See Figure 8).
Current Address Byte Read
The SMS2916 contains an internal address counter
which maintains the address of the last word accessed,
incremented by one. If the last address accessed (either
a read or write) was to address location n, the next read
operation would access data from address location n+1
and increment the current address pointer. When the
SMS2916 receives the slave address field with the R/W
bit set to “1,” it issues an acknowledge and transmits the
8-bit word stored at address location n+1.
Internal WRITE Cycle
In Progress;
Begin ACK Polling
Issue Start
Issue Slave
Address and
R/W = 0
ACK
Returned?
Issue Stop
No
The current address byte read operation only accesses a
single byte of data. The master does not acknowledge the
transfer, but does generate a stop condition. At this point,
the SMS2916 discontinues data transmission. See Figure 9 for the address acknowledge and data transfer
sequence.
Yes (Internal WRITE Cycle is completed)
Next
operation a
WRITE?
No
Yes
Issue Byte
Address
Issue Stop
Proceed with
WRITE
Await Next
Command
Current Address Byte Read
Random Address Byte Read
Current Address Sequential Read
Random Address Sequential Read
2028 ILL10.0
FIGURE 8. ACKNOWLEDGE POLLING
SDA Bus Activity
X X X R
W
1
1 0 1 0
S
T Device
Type
A Address
R
T
1
Read/Write
1= Read
Slave Address
Master sends Read
request to Slave
Master Transmitter
to
Slave Receiver
A
C
K
Data Byte
D D D D D D D D
7 6 5 4 3 2 1 0
1
Lack of ACK (low)
from Master
determines last
data byte to be read
S
T
O
P
Slave sends
Data to Master
Slave Transmitter
to
Master Receiver
Shading Denotes
SMS2916
SDA Output Active
2028 ILL11.0
FIGURE 9. CURRENT ADDRESS BYTE READ MODE
2028-02 4/24/98
9
SMS2916
Preliminary
Random Address Byte Read
Random address read operations allow the master to
access any memory location in a random fashion. This
operation involves a two-step process. First, the master
issues a write command which includes the start condition and the slave address field (with the R/W bit set to
WRITE) followed by the address of the word it is to read.
This procedure sets the internal address counter of the
SMS2916 to the desired address.
SDA Bus
Activity
A A X R
10 9
W
1 0 1 0
S
T Device
Type
A Address
R
T
A A
10 9 X
0
A
C
K
After the word address acknowledge is received by the
master, the master immediately reissues a start condition
followed by another slave address field with the R/W bit
set to READ. The SMS2916 will respond with an acknowledge and then transmit the 8-data bits stored at the
addressed location. At this point, the master does not
acknowledge the transmission but does generate the stop
condition. The SMS2916 discontinues data transmission
and reverts to its standby power mode. See Figure 10 for
the address, acknowledge and data transfer sequence.
A
C
K
Word Address
A A A A A A
7 6 5 4 3 2
A A
1 0
Slave Address
Master Transmitter
to
Slave Receiver
Shading Denotes
SMS2916
SDA Output Active
1 0 1 0
S
T Device
Type
A Address
R
T
Read/Write
0= Write
Master sends Read
request to Slave
X X X R
W
1
Read/Write
1= Read
Slave Address
Master Writes Word
Address to Slave
Master Requests
Data from Slave
Master Transmitter
to
Slave Receiver
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
A
C
K
Data Byte
D D D D D D D D
7 6 5 4 3 2 1 0
1
Lack of ACK (low)
from Master
determines last
data byte to be read
Slave sends
Data to Master
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
2028 ILL12.0
FIGURE 10. RANDOM ADDRESS BYTE READ MODE
2028-02 4/24/98
10
S
T
O
P
SMS2916
Preliminary
Sequential READ
Sequential READs can be initiated as either a current
address READ or random access READ. The first word is
transmitted as with the other byte read modes (current
address byte READ or random address byte READ);
however, the master now responds with an ACKnowledge,
indicating that it requires additional data from the
SMS2916. The SMS2916 continues to output data for
each ACKnowledge received. The master terminates the
sequential READ operation by not responding with an
ACKnowledge, and issues a STOP conditions.
During a sequential read operation, the internal address
counter is automatically incremented with each acknowledge signal. For read operations, all address bits are
incremented, allowing the entire array to be read using a
single read command. After a count of the last memory
address, the address counter will ‘roll-over’ and the
memory will continue to output data. See Figure 11 for the
address, acknowledge and data transfer sequence.
Acknowledge from
Master Receiver
Acknowledges from SMS2916
SDA Bus
Activity
A A
R
X
10 9
W
A A
9 X
1 0 1 0 10
S
T Device
A Type
R Address
T
0
A
C Word Address
K
A A A A A A A A
7 6 5 4 3 2 1 0
Slave Address
Master Transmitter
to
Slave Receiver
X X
X
1 0 1 0
S
T Device
A
Type
R Address
T
Read/Write
0= Write
Master sends Read
request to Slave
A
C
K
R
W
1
A
C
K
A
First Data Byte C
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
D D D D D D D D
7 6 5 4 3 2 1 0
D D D D D D D D
7 6 5 4 3 2 1 0
1
S
T
O
P
Read/Write
1= Read
Master Requests
Data from Slave
Master Transmitter
to
Slave Receiver
Slave Transmitter
to
Master Receiver
Last Data Byte
K
Lack of ACK (low)
determines last
data byte to be read
Slave Address
Master Writes Word
Address to Slave
Lack of
Acknowledge from
Master Receiver
Slave sends
Data to Master
Slave Transmitter
to
Master Receiver
Slave Transmitter
to
Master Receiver
Slave sends
Data to Master
Slave Transmitter
to
Master Receiver
Master Transmitter
to
Slave Receiver
Shading Denotes
SMS2916
SDA Output Active
2028 ILL13.0
FIGURE 11. SEQUENTIAL READ OPERATION (starting with a Random Address READ)
2028-02 4/24/98
11
SMS2916
Preliminary
S
T
A
R
T1010x x x
S
T
A
R
T1010x x x
S
T
O
P
R
W
S
T
A
R
T1010x x x
S
T
O
P
R
W
SCL and SDA Idle
S
T
O
P
R
W
SCL and SDA Idle
A
C
K
A
C
K
A
C
K
tPURST
ACK response from SMS2916
Resets The Watchdog Timer
RESET
t < 1.6sec
t > 1.6sec
t0
t0
t0
2028 ILL14.1
FIGURE 12. SEQUENCE ONE
S
T
A
R
T1010x x x
S
T
A
R
T1010x x x
S
T
O
P
R
W
SCL and SDA Idle
R
W
S
T
O
P
SCL and SDA Idle
A
C
K
A
C
K
No Affect On tPURST
Watchdog Timer t0
tPURST
RESET
t > 1.6sec
t > 1.6sec
t0
t0
2028 ILL15.0
FIGURE 13. SEQUENCE TWO
2028-02 4/24/98
12
SMS2916
Preliminary
Frequently the supervisory circuit will be deployed on a PC board that provides a peripheral function to a system.
Examples might be modem or network cards in a PC or a PCMCIA card in a laptop. In instances like this the peripheral
card may have a requirement for a clean reset function to insure proper operation. The system may or may not provide
a reset pulse of sufficient duration to clear the peripheral or to protect data stored in a nonvolatile memory.
The I/O capability of the RESET pins can provide a solution. The system’s reset signal to the peripheral can be fed
into the SMS2916 and it in turn can clean up the signal and provide a known entity to the peripheral’s circuits. The
figure below shows the basic timing characteristics under the assumption the reset input is shorter in duration than
tPURST. The same reset output affect can be attained by using the active high reset input.
RESET
Input
RESET
Output
RESET
Output
t PURST
2028 ILL16.0
If you happen to be using one of the more common supervisory circuits like a 1232, you might consider reducing your
component count such as illustrated below.
+5VDC
From This
8051 Family Part
PBRST
1232
Vcc
+5VDC
ST
ALE
To This
TOL RST
GND RST
RST
VCC
24C16
SCL
I/O
GND SDA
I/O
8051 Family Part
ALE
SMS2916
WDI
RST
RST
RST
I/O
GND
SCL
SDA
I/O
2028 ILL18.1
2028-02 4/24/98
13
SMS2916
Preliminary
8 Pin PDIP (Type P) Package
.375
(9.525)
.250
(6.350)
PIN 1 INDICATOR
.300 (7.620)
.070 (1.778)
.0375 (0.952)
.015 (.381) Min.
5°-7°TYP.
(4 PLCS)
0°-15°
SEATING PLANE
.130 (3.302)
.060 ± .005
(1.524) ± .127
TYP.
.100 (2.54)
TYP.
.130 (3.302)
.018 (.457)
TYP.
.350 (8.89)
.009 ± .002
(.229 ± .051)
8pn PDIP/P ILL.3
8 Pin SOIC (Type S) Package JEDEC (150 mil body width)
.050 (1.27) TYP.
.050 (1.270) TYP.
8 Places
.157 (4.00)
.150 (3.80)
.275 (6.99) TYP.
.030 (.762) TYP.
8 Places
1 .196 (5.00)
.189 (4.80)
FOOTPRINT
.061 (1.75)
.053 (1.35)
.020 (.50) x45°
.010 (.25)
.0192 (.49)
.0138 (.35)
.0098 (.25)
.004 (.127)
.05 (1.27) TYP.
.035 (.90)
.016 (.40)
.244 (6.20)
.228 (5.80)
8pn JEDEC SOIC ILL.2
2028-02 4/24/98
14
SMS2916
Preliminary
ORDERING INFORMATION
SMS2916 P
I -2.7
T
Tape and Reel Option
Blank = Bulk
T = Tape & Reel
Base Part Number
Package
P = 8 Lead PDIP
S = 8 Lead 150mil SOIC
Operating Voltage Range
A = 4.5V to 5.5V VTRIP Min. @ 4.25V
B = 4.5V to 5.5V VTRIP Min. @ 4.50V
2.7 = 2.7V to 5.5V VTRIP Min. @ 2.55V
Operating Temperature Range
Blank = 0°C to +70°C
I = -40°C to +85°C
2028 ILL17.0
2028-02 4/24/98
15
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