Information Technology Reference
In-Depth Information
Bus plane contains ECL buffers for
clock distribution
Slot 0 (Generates bus clocks)
Slot 1
Slot 2
Slot 12
Figure 22.5
VMI clock distribution
Slot 3
Slot 2
Slot 1
Slot 0
Slot 12
Equal
distance
between all
the slots and
slot 0
STARX
STARY
Figure 22.6
VMI clock distribution
22.4.3 Trigger bus
The trigger bus is a general-purpose logic bus that can be used for triggering, handshaking,
clocking or data transmission. It uses eight TTL trigger lines and six ECL trigger lines.
22.4.4 Local bus
The local bus is used for intercommunication between two or more modules that does not use
a global bus. It has 72 lines on each module, which are partitioned into 36 lines on each side
of the module, as illustrated in Figure 22.7. The purpose of the bus is to decrease the need for
jumpers between modules and to provide local communications between two or more mod-
ules without using a global bus. For example, two cards could be placed in consecutive sock-
ets and communicate with each other using the right-hand side pins on left-most card and the
left-hand side pins on the right-most card.
