Contemporary-control-systems EXP Expansion Modules User Manual Uživatelský manuál stáhnout pdf (Strana 27)

accommodate this signal generation while maintaining

compatibility with coaxial and fiber optic signals.

Timers

A simple crystal oscillator and divider are used to develop the

unlatch delay time and reconfiguration timers. Although not

critical, the unlatch delay timer is more repeatable from a

crystal oscillator. However, the reconfiguration timer is more

critical. The reconfiguration timer does not sense a

reconfiguration on the network, it only predicts that a

reconfiguration will occur. This is accomplished by noting that

no data has occurred for 82 µs (at standard timeouts). Once this

timer is exceeded, the yellow RECON LED is lit for about

950 ms. If the hub is operated on a network with extended

ARCNET timeouts, jumpers must be set on the timing module

to extend the reconfiguration timer to match the network

timeouts. There are a total of four jumper settings

corresponding to the four possible timeouts.

Watchdog Timer

If no hub activity is sensed after a predetermined time, a

watchdog timer will automatically reset the MOD HUB timing

module. This is to ensure that the hub reestablishes

communication after a significant electrostatic or

electromagnetic phenomenon without requiring any human

intervention.

TD401600-0MO

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Contemporary-control-systems EXP Expansion Modules User Manual Uživatelský manuál Strana 27