SC1100 Datasheet, PDF (56/348 Pages) National Semiconductor (TI) – Geode™ Information Appliance On a Chip

General Configuration Block (Continued)
WATCHDOG Interrupt
The WATCHDOG interrupt (if configured and enabled) is
routed to an IRQ signal. The IRQ signal is programmable
via the INTSEL register (Offset 38h, described in Table 3-2
"Multiplexing, Interrupt Selection, and Base Address Regis-
ters" on page 50). The WATCHDOG interrupt is a share-
able, active low, level interrupt.
WATCHDOG SMI
The WATCHDOG SMI is recognized by the Core Logic
module as internal input signal EXT_SMI0#. To use the
WATCHDOG SMI, Core Logic registers must be configured
appropriately.
3.3.2 WATCHDOG Registers
Table 3-3 describes the WATCHDOG registers.
3.3.2.1 Usage Hints
• SMM code should set bit 8 of the WDCNFG register to 1
when entering ACPI C3 state, if the WATCHDOG timer
is to be suspended. If this is not done, the WATCHDOG
timer is functional during C3 state.
• SMM code should set bit 8 of the WDCNFG register to
1, when entering ACPI S1 and S2 states if the
WATCHDOG timer is to be suspended. If this is not
done, the WATCHDOG timer is functional during S1 and
S2 states.
Table 3-3. WATCHDOG Registers
Bit
Description
Offset 00h
Width: WORD
WATCHDOG Timeout Register - WDTO (R/W)
This register specifies the programmed WATCHDOG timeout period.
Reset Value: 0000h
15:0 Programmed timeout period.
Offset 02h
Width: WORD
WATCHDOG Configuration Register - WDCNFG (R/W)
Reset Value: 0000h
This register selects the signal to be generated when the timer reaches 0, whether or not to disable the 32 KHz input clock during low
power states, and the prescaler value of the clock input.
15:9 Reserved. Write as read.
8
WD32KPD (WATCHDOG 32 KHz Power Down).
0: 32 KHz clock is enabled.
1: 32 KHz clock is disabled, when the GX1 module asserts its internal SUSPA# signal.
This bit is cleared to 0, when POR# is asserted or when the GX1 module deasserts its internal SUSPA# signal (i.e., on
SUSPA# rising edge). See Section 3.3.2.1 "Usage Hints" on page 56.
7:6 WDTYPE2 (WATCHDOG Event Type 2).
00: No action
01: Interrupt
10: SMI
11: System reset
This field is reset to 0 when POR# is asserted. Other system resets do not affect this field.
5:4 WDTYPE1 (WATCHDOG Event Type 1).
00: No action
01: Interrupt
10: SMI
11: System reset
This field is reset to 0 when POR# is asserted. Other system resets do not affect this field.
3:0 WDPRES (WATCHDOG Timer Prescaler). Divide 32 KHz by:
0000: 1
0100: 16
1000: 256
1100: 4096
0001: 2
0101: 32
1001: 512
1101: 8192
0010: 4
0110: 64
1010: 1024
1110: Reserved
0011: 8
0111: 128
1011: 2048
1111: Reserved
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