Local Bus Signal Routing; Reset Circuit; Interrupt - Racal Instruments X Series Manual

1260-100X User Manual
Local Bus Signal
Routing

Reset Circuit

Interrupt

Racal Instruments © 2005
The Backplane/Mezzanine PCB subassembly provides the bridge
circuitry to interface between the plug-ins and the Option-01T. It
receives the local bus signals from the Option-01T on connector
P2A.
The local bus signals LBUSC00S through LBUSC09S are
differential. U4 and U5 converts LBUSC00S through LBUSC07S
to TTL levels. LBUSC08S and LBUSC09S are a bidirectional
differential pair. U5 and U8 receive and drive these signals,
respectively.
U1 is a voltage monitor used to reset the Bridge and plug-ins at
power turn-on. At power turn-on, it drives LLOGICRST low for
approximately 130ms. It then takes LLOGICRST high and leaves
it high, unless +5V power drops below 4.5V.
The signal LBUSC10S is an open-collector line from the
Option-01T. During power turn-on, the Option-01T drives
LBUSC10S low for about 100ms, then allows it to be pulled high.
While LBUSC10S is low, it resets all relay drivers on all plug-ins to
the inactive state, opening all relays. It also clears all outputs on
digital test plug-ins to a known state.
LBUSC10S also serves another function when a plug-in asserts a
global reset during an emergency reset event. When such an
event occurs, the plug-in drives LBUSC10S low. It leaves it low
until the event has passed and the Option-01T firmware clears the
reset latch in the plug-in.
LBUSC10S also connects to all other devices controlled by the
same Option-01T. When any device in this group asserts a global
reset, all devices in the group respond by resetting their drivers.
The signal LBUSC11S is an open-collector line to the Option-01T.
It has two purposes. When a plug-in asserts an emergency reset
condition, it drives the LBUSC11S signal low. Also, the 1260-114
drives the LBUSC11S signal low to announce a synchronous
event. When LBUSC11S goes low, the Option-01T polls the plug-
ins to determine which one generated the interrupt.
responds accordingly.
1260-100X Theory of Operation B-3
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