ne1618 NXP Semiconductors, ne1618 Datasheet - Page 10

• Manufacturer Part Number: ne1618
• Description: Temperature Monitor For Microprocessor Systems
• Manufacturer: NXP Semiconductors

and bit 6 is used to activate the standby software mode when this bit
Philips Semiconductors
Configuration register
The configuration register is used to mask the Alert interrupt and/or
to put the device in software standby mode. Only two bits 6 and 7 of
this register are used as listed in Table 5. Bit 7 is used to mask the
device ALERT output from Alert interruption when this bit is set to 1,
is set to to 1.
This register can be written or read using the commands of registers
named WC and RC accordingly. Upon power-on reset (POR), both
bits are reset to zero.
Table 5. Configuration register bit assignments
Conversion rate register
The conversion rate register is used to store programmable
conversion data, which defines the time interval between
conversions in standard free-running auto-convert mode. Table 6
shows all applicable data and rates for the device. Only three LSB
bits of the register are used and other bits are reserved for future
use. This register can be written to and read back over the SMBus
using commands of the registers named WCR and RCR
respectively. The POR default conversion data is 02h.
Because of the timing asynchronization, when changing the
conversion rate from fast to slow, or vice versa, you may get an
invalid data for the external temp reading, and an Alert interruption
as well. Therefore, caution must be taken when doing a change of
conversion rate. Changing conversion should be done in one of the
following ways:
1. Apply this sequential operation:
2. Writing the conversion data to the conversion register WCR
We suggest that method “1.” is preferred because it will provide the
correct temp data in a defined time. Releasing the device from
shutdown mode by clearing bit6 of the WC register also initiates a
new conversion, and all the register data will be updated at the end
2002 Jan 04
7 (MSB)
Temperature monitor for microprocessor systems
5 to 0
a. Put the device into its standby mode (by setting bit6 of the
b. Wait at least 750 ms (to ensure the current conversion if
c. Change the conversion rate (by writing the conversion data
d. Put the device back into its normal mode (by clearing bit6 of
when the busy bit is off. The busy bit can be monitored by
reading the Status Register (SR) bit 7.
BIT
6
WC register).
there is one to be completed).
into the WCR register).
the WC register).
RESERVED
RUN/STOP
NAME
MASK
STATE
POR
n/a
0
0
When LOW, running mode is
Mask ALERT interrupt:
Interrupt is enabled when
this bit is LOW, and disabled
when this bit is HIGH.
Standby or run mode
control:
enabled. When HIGH,
standby mode is initiated.
n/a
FUNCTION
10
or exceeds the corresponding temperature limits, an Alert interrupt is
of the conversion in 750 ms (max.) for slow rate, and 170 ms for fast
rate.
The device will be automatically put into the extended measurement
mode when the conversion rate data is less than or equal to 04h.
Otherwise, it will be in basic measurement mode for the remote
temp.
Notice that the average supply current, as well as the device power
consumption, is increased with the conversion rate.
Table 6. Conversion rate control byte
Temperature limit registers
The device has four registers to be used for storing programmable
temperature limits, including the high limit and the low limit for each
channel of the external and internal diodes. Data of the temperature
register (RIT and RET) for each channel are compared with the
contents of the temperature limit registers of the same channel,
resulting in alarm conditions. If measured temperature either equals
asserted and the corresponding flag bit in the status register is set.
The temperature limit registers can be written to and read back
using commands of registers named WIHL, WILL, WEHL, WELL,
RIHL, RILL, REHL, RELL accordingly. The POR default values are
+127 C (0111 1111) for the HIGH limit and –55 C (1100 1001) for
the LOW limit.
Notice that only the RET data is used in limit comparison and REET
data is ignored.
One-shot command
The one shot command is not actually a data register as such and a
write operation to it will initiate an ADC conversion. The send byte
format of the SMBus, as described later, with the use of OSHT
command (0Fh), is used for this writing operation. In normal
free-running-conversion operation mode of the device, a one-shot
command immediately forces a new conversion cycle to begin.
However, if a conversion is in progress when a one-shot command
is received, the command is ignored. In software standby mode, the
one-shot command generates a single conversion and comparison
cycle and then puts the device back in its standby mode after the
conversion. In hardware standby mode, the one shot is inhibited.
Notice that a one-shot command will clear the REET register and
set a basic measurement for that cycle.
08h to FFh
DATA
00h
01h
02h
03h
04h
05h
06h
07h
CONVERSION
RATE (Hz)
Reserved
0.06
0.12
0.22
0.40
0.70
2
4
8
( A Typ. @ V
SUPPLY CURRENT
AVERAGE
TBD
TBD
TBD
TBD
TBD
TBD
TBD
TBD
n/a
NE1618
DD
Product data
= 3.3 V)