Pentek 6230 Operating Manual page 211

INTERRUPT STATUS MIRROR REGISTERS
Whenever a bit in one of the Interrupt Status Registers is updated,
the same bit is written to duplicate registers at addresses 4Ch
and 42h. These registers allow a second management system to
access the status data without worrying about clearing the data.
The data in these registers is for reading only and has no effect
on the interrupt output.
TEMPERATURE INTERRUPT MODES
The ADM1024 has two distinct methods of producing interrupts
for out-of-limit temperature measurements from the internal or
external sensors. Temperature errors can generate an interrupt
on the INT pin along with other interrupts, but there is also
a separate THERM pin that generates an interrupt only for
temperature errors.
Operation of the INT output for temperature interrupts is
illustrated in Figure 15. Assuming that the temperature starts off
within the programmed limits and that temperature interrupt
sources are not masked, INT will go low if the temperature
measured by any of the internal or external sensors exceeds the
programmed high temperature limit for that sensor, or the hard-
ware limits in register 13h, 14h, 17h, or 18h.
100 C
90 C
80 C
*
70 C
TEMP
60 C
*
50 C
40 C
INT
ACPI CONTROL
METHODS
CLEAR EVENT
*ACPI AND DEFAULT CONTROL METHODS
ADJUST TEMPERATURE LIMIT VALUES
Figure 15. Operation of INT for Temperature Interrupts
Once the interrupt has been cleared, it will not be reasserted
even if the temperature remains above the high limit(s). However,
INT will be reasserted if:
a. the temperature falls below the low limit for the sensor
or
b. the high limit is/are reprogrammed to a new value, and the
temperature then rises above the new high limit on the next
monitoring cycle
or
c. the THERM pin is pulled low externally, which sets Bit 5 of
Interrupt Status Register 2
or
d. An interrupt is generated by another source.
Similarly, should the temperature measured by a sensor start off
within limits then fall below the low limit, INT will be asserted.
Once cleared, it will not be reasserted unless:
REV. A
*
HIGH LIMIT
*
*
LOW LIMIT
*
a. the temperature rises above the high limit
or
b. the low limit is/are reprogrammed, and the temperature then
falls below the new low limit
or
c. the THERM pin is pulled low externally, which sets Bit 5 of
Interrupt Status Register 2
or
d. an interrupt is generated by another source.
THERM INPUT/OUTPUT
The Thermal Management Input/Output (THERM) is a logic
input/output with an internal, 100 kΩ pull-up resistor, that
provides a separate output for temperature interrupts only. It is
enabled by setting Bit 2 of Configuration Register 1. The THERM
output has two operating modes that can be programmed by Bit
3 of Configuration Register 2 (address 4Ah). With this bit set to
the default value of 0, the THERM output operates in "Default"
interrupt mode. With this bit set to 1, the THERM output oper-
ates in "ACPI" mode.
Thermal interrupts can still be generated at the INT output
while THERM is enabled, but if these are not required they can
be masked by writing a 1 to bit 0 of Configuration Register 2
(address 4Ah). The THERM pin can also function as a logic
input for an external sensor, for example a temperature sensor such
as the ADM22105 used in Figure 16b. If THERM is taken low
by an external source, the analog output will be forced to FFh to
switch a controlled fan to maximum speed. This also generates
an INT output as previously described.
DEFAULT MODE
In Default mode, the THERM output operates like a thermostat
with hysteresis. THERM will go low and Bit 5 of Interrupt Status
Register 2 will be set, if the temperature measured by any of
the sensors exceeds the high limit programmed for that sensor.
It will remain asserted until reset by reading Interrupt Status
Register 2, by setting Bit 6 of Configuration Register 1, or
when the temperature falls below the low limit programmed
for that sensor.
TEMP
HIGH LIMIT
TEMP
TEMP
LOW LIMIT
THERM
PROGRAMMED
VALUE
ANALOG
OUTPUT
Figure 16a. INT or THERM Output in Default Mode
–19–
ADM1024
CLEARED BY
CLEARED BY
READ OR TEMP FALLING
THERM CLEAR
BELOW LOW
LIMIT FF
H
EXT
THERM
INPUT