NE1618DS View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
NE1618DS Datasheet PDF : 16 Pages
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Philips Semiconductors
Temperature monitor for microprocessor systems
Product data
NE1618
Status register
The content of the status register reflects condition status resulting
from all of these activities: comparisons between temperature
measurements and temperature limits, the status of ADC
conversion, and the hardware condition of the connection of external
diode to the device. Bit assignments and bit functions of this register
are listed in Table 7. This register can only be read using the
command of register named RS. Upon POR, the status of all flag
bits are reset to zero. The status byte is cleared by any successful
read of the status register unless the fault condition persists.
Notice that any one of the fault-conditions, except the conversion
busy, also introduces an Alert interrupt to the SMBus that will be
described in the following section. Also, whenever a one-shot
command is executed, the status byte should be read after the
conversion is completed, which is about 170 ms after the one-shot
command is sent.
Table 7. Status register bit assignment
BIT
NAME
POR
STATE
FUNCTION
7 (MSB) BUSY n/a High when the ADC is busy
converting
6
IHLF*
0
High when the internal
temperature high limit has tripped
5
ILLF*
0
High when the internal
temperature low limit has tripped
4
EHLF*
0
High when the external
temperature high limit has tripped
3
ELLF*
0
High when the external
temperature low limit has tripped
2
OPEN*
0
High when the external diode is
SHORT
opened or shorted
1 to 0
n/a
0
Reserved
* These flags stay high until the status register is read or POR is
activated.
Alert interrupt
The ALERT output is used to signal Alert interruption from the
device to the SMBus and is active low. Because this output is an
open-drain output, a pull-up resistor (10 kΩ typ.) to VDD is required,
and slave devices can share a common interrupt line on the same
SMBus. An Alert interrupt is asserted by the device whenever any
one of the fault conditions, as described in the Status register
section, occurs: measured temperature equals or exceeds
corresponding temp limits, the remote diode is physically
disconnected from the device pins. Alert interrupt signal is latched
and can only be cleared by reading the Alert Response byte from
the Alert Response Address which is a special slave address to the
SMBus. The ALERT output can not be reset by reading the device
status register. The device was designed to accommodate the Alert
interrupt detection capability of the SMBus.
Basically, the SMBus provides Alert response interrupt pointers in
order to identify the slave device which has caused the Alert
interrupt. The 7-bit Alert slave address is 0001 100 and the Alert
response byte reflects the slave address of the device which has
caused Alert interrupt. Bit assignments of the Alert response byte
are listed in Table 8. The ALERT output will be reset to HIGH state
upon reading the Alert response slave address unless the fault
condition persists.
Table 8. Alert response bit assignment
(Alert response address = 0001 100)
ALERT
NAME
RESPONSE ADDRESS
BIT
BIT
FUNCTION
7 (MSB)
ADD7 Indicate address B6 of alerted device
6
ADD6 Indicate address B5 of alerted device
5
ADD5 Indicate address B4 of alerted device
4
ADD4 Indicate address B3 of alerted device
3
ADD3 Indicate address B2 of alerted device
2
ADD2 Indicate address B1 of alerted device
1
ADD1 Indicate address B0 of alerted device
0 (LSB)
1
Logic 1
Fault detection
The NE1618 has a fault detector to the diode connection. The
connection is checked when a conversion is initiated and the proper
flags are set if the fault condition has occurred.
D+ & D–
Opened
Shorted
ALERT
OUTPUT
Low
Low
RET DATA
STORAGE
–128°C
–128°C
STATUS SET
FLAG
B2 & B3
B2 & B3
SMBus interface
The device can communicate over a standard 2-wire serial interface
System Management Bus (SMBus) using the device pins SCLK and
SDATA. The device employs four standard SMBus protocols: Write
Byte, Read Byte, Send Byte and Receive Byte. Data formats of
those protocols are shown in Table 9 with following notifications:
– The SMBus master initiates data transfer by establishing a start
condition (S) and terminates data transfer by generating a stop
condition (P).
– Data is sent over the serial bus in sequence of 9 clock pulses
according to each 8-bit data byte followed by 1-bit status of the
device acknowledgement (A).
– The 7-bit slave address is equivalent to the selected address of
the device.
– The command byte is equivalent to the selected command of the
device register
– The send byte format is often used for the one-shot conversion
command.
– The receive byte format is used for quicker transfer data from a
device reading register which was previously selected by a read
byte format.
2002 Jan 04
11
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