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PT0289(07/07)

Ver: 0

6

To minimize data loss and speed system recovery,

many applications interrupt the processor or reset

only portions of the system before processor hard

reset is asserted. The extended setup time of the

PT7M7443~7452 manual reset inputs allows the

same pushbutton (connected to both the processor

interrupt and the extended /MR1 input, as shown in

Figure 15) to control both the interrupt and hard

reset functions. If the pushbutton is closed for less

than 6.72s, the processor is only interrupted. If the

system still does not respond properly, the

pushbutton (or two buttons for the dual manual reset)

can be closed for the full extended setup period to

hard reset the processor. If desired, connect an LED

to the /RESET output to blink off (or on) for the

reset timeout to signify when the pushbutton is

closed long enough for a hard reset) the same LED

might be used as the front-panel power-on display).

The PT7M7447/7448/7451/7452 dual manual

resets are useful in applications in which both an

extended and immediate setup periods are needed.

Figure 16 illustrates the insertion and removal of a

smart

card.

/MR1

monitors

a

front-panel

pushbutton. When closed for 6.72s, /RESET one-

shot pulses low for 140ms min. Because /MR1 is

the front-panel switch can be connected to a

microprocessor for general-purpose I/O control.

MR2 monitors a switch to detect when a smart card

is inserted. When the switch is closed high (card

inserted), /RESET one-shot pulses low for 140ms.

MR2 is internally debounced for 210ms to prevent

false resets when the smart card is removed.