SMS64 datasheet(14/24 Pages) SUMMIT

14 / 24 page

SMS64

Preliminary

Summit Microelectronics, Inc

2060 2.22 10/09/03

WATCHDOG AND LONGDOG TIMERS

The SMS64 contains two timers that can be

programmed independently. The Watchdog timer will

generate an interrupt if it times out. The Longdog timer

will generally be programmed to be of longer duration

than the Watchdog timer and will generate a reset if it

times out. Both timers are cleared by a low to high

transition on WLDI and start simultaneously.

If the Longdog times out RST_A# and RST_B# will

be driven low either until a WLDI clear is received or

until tPRTO (whichever occurs first), at which time they

will return high. When RST_A# and RST_B# return

high both timers are reset to time zero. Therefore, if

the Longdog tPLDTO is shorter than the Watchdog

tPWDTO, RST_A# and RST_B# will effectively clear the

interrupt before it can drive the output low

If WLDI is held low the timers will free-run

generating a series of interrupts and resets. If WLDI is

held high the interrupt (Watchdog) output will be

disabled and only the reset (Longdog) outputs will be

active.

Refer to Figure 6 which illustrates the action of

RST_A#, RST_B# and IRQ# with respect to the

Watchdog and Longdog timers and the WLDI input.

PRTO

PLDTO

PWDTO

PLDTO

PRTO

RST_A#

RST_B#

IRQ#

WLDI

Figure 6. Watchdog, Longdog and WLDI Timing Diagram

APPLICATIONS INFORMATION (CONTINUED)

SMS64 bảng dữ liệu(PDF) 14 Page - Summit Microelectronics, Inc.