AMD SC1200 Watchdog Registers, Watchdog Interrupt, 3describes the Watchdog registers, Usage Hints

32579B General Configuration Block

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 4-2 "Pin Multiplexing, Interrupt Selection, and Base Address Registers" on page 72). The WATCHDOG interrupt is a shareable, 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.

4.3.2WATCHDOG Registers

Table 4-3describes the WATCHDOG registers.

4.3.2.1Usage 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 4-3. WATCHDOG Registers

Bit	Description
Offset 00h-01h		WATCHDOG Timeout Register - WDTO (R/W)	Reset Value: 0000h
This register specifies the programmed WATCHDOG timeout period.
15:0	Programmed timeout period.
Offset 02h-03h		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 de-asserts its internal SUSPA# signal (i.e., on
	SUSPA# rising edge). See Section 4.3.2.1 "Usage Hints" on page 80.
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

80 AMD Geode™ SC1200/SC1201 Processor Data Book