PC expansion bus systems - PC Based Instrumentation and Control - page 80

Pin Name Description Pin Name Description

A86 AD38 Address/Data 38 B86 AD39 Address/Data 39

A87 GND Ground B87 AD37 Address/Data 37

A88 AD36 Address/Data 36 B88 + 5 V Power ( + 5V or + 3.3 V)

A89 AD34 Address/Data 34 B89 AD35 Address/Data 35

A90 GND Ground B90 AD33 Address/Data 33

A91 AD32 Address/Data 32 B91 GND Ground

A92 RES Reserved B92 RES Reserved

A93 GND Ground B93 RES Reserved

A94 RES Reserved B94 GND Ground

Notes:
1

Signals on pins 63 to 94 are only used on 64-bit PCI bus cards.

2 The copper foil side of the card is side A whilst the component side is side B.

3 A # used after a signal name indicates that the signal in question is active

low (or asserted low).

4 The time-multiplexed address and data bus may exist as either 0 to 31 bits

(32 bits) or 0 to 63 bits (64 bits) using the 64-bit expansion bus. Both address
and data signals use the same bus; addresses followed by data. A 32-bit PCI
may also use 64-bit addressing by using two address cycles, referred to as
Dual Address Cycles (DAC), in which the low order address is sent first.
Additional control bits are used when the bus is used in 64-bit mode.

5 The bus connectors are labelled ' + 5V or + 3.3 V' in the case of + 5 V systems

and ' + 3.3 V' for 3.3 V systems. Note that the original PCI standard required
that plug-in boards use + 5 V supplies provided by the PCs motherboard. As
the PCI standard evolved, the option was added for a + 3.3 V power source.
Furthermore, the newer PCI 2.3 standard has now made the + 5 V supply
obsolete. This means that many of the most recent PCs can only accept 3.3 V
or 'universal' PCI cards. Contacts on the PCI connector (keyways A12, B12,
etc.) are used to determine the correct power rail voltages (see Figure 2.2).

Photo 2.13 Five PCI expansion connectors in a modern PC