SCH3112 Datasheet, PDF (212/396 Pages) SMSC Corporation – LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports

23.9.4
LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
The enable bit is located in the SMI_EN5 register at offset 1Ah.
Datasheet
The SMI is enabled onto the SERIRQ (IRQ2) via bit 6 of the SMI_EN2 register at 17h.
Interrupt Event on Serial IRQ
The hardware monitoring interrupt signal is routed to the Serial IRQ logic. This signal is unaffected by
the nHWM_INT pin enable (INT_EN) bit (See Figure 23.3 Interrupt Control on page 193.)
This operation is configured via the Interrupt Select register (0x70) in Logical Device A. This register
allows the selection of any serial IRQ frame to be used for the HWM nHWM_INT interrupt (SERIRQ9
slot will be used). See Interrupt Event on Serial IRQ on page 196.
23.10
Low Power Mode
The hardware monitor has two modes of operation: Monitoring and Sleep. When the START bit,
located in Bit[0] of the Ready/Lock/Start register (0x40), is set to zero the hardware monitor is in Sleep
Mode. When this bit is set to one the hardware monitor is fully functional and monitors the analog
inputs to this device.
Sleep mode is a low power mode in which bias currents are on and the internal oscillator is on, but
the the A/D converter and monitoring cycle are turned off. Serial bus communication is still possible
with any register in the Hardware Monitor Block while in this low-power mode.
Notes:
■ In Sleep Mode the PWM Pins are held high forcing the PWM pins to 100% duty cycle (256/256).
■ The START a bit cannot be modified when the LOCK bit is set.
23.11 Temperature Measurement
Temperatures are measured internally by bandgap temperature sensor and externally using two sets
of diode sensor pins (for measuring two external temperatures). See subsections below.
Note: The temperature sensing circuitry for the two remote diode sensors is calibrated for a 3904
type diode.
23.11.1 Internal Temperature Measurement
Internal temperature can be measured by bandgap temperature sensor. The measurement is
converted into digital format by internal ADC. This data is converted in two’s complement format since
both negative and positive temperature can be measured. This value is stored in Internal Temperature
Reading register (26h) and compared to the Temperature Limit registers (50h – 51h). If this value
violates the programmed limits in the Internal High Temperature Limit register (51h) and the Internal
Low Temperature Limit register (50h) the corresponding status bit in Interrupt Status Register 1 is set.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See the
section titled Auto Fan Control Operating Mode on page 201.
23.11.2 External Temperature Measurement
The Hardware Monitor Block also provides a way to measure two external temperatures using diode
sensor pins (Remote x+ and Remote x-). The value is stored in the register (25h) for Remote1+ and
Remote1- pins. The value is stored in the Remote Temperature Reading register (27h) for Remote2+
and Remote2- pins. If these values violate the programmed limits in the associated limit registers, then
the corresponding Remote Diode 1 (D1) or Remote Diode 2 (D2) status bits will be set in the Interrupt
Status Register 1.
Rev 0.2 (09-28-04)
196
DATASHEET
SMSC SCH311X