PC expansion bus systems - PC Based Instrumentation and Control - page 95

Figure 2.21 USB cable
connector

Figure 2.24 USB pin connections

• The Series 'B' receptacle mates with a Series 'B' plug (male). Electrically,
Series 'B' receptacles function as inputs to hubs or devices.
• The Series 'B' plug mates with a Series 'B' receptacle. The Series 'B' plug
is always oriented towards the USB hub or device.

Figure 2.22 USB connector
(type A)

Full-speed devices can utilize the 'B' connector. This allows the device to
have a detachable USB cable. This eliminates the need to build the device with
a hardwired cable and minimizes end user problems if cable replacement is
necessary. Figure 2.21 shows a typical Series 'A' connector showing the USB
icon and the top locator (a small 'pip' located towards the cable end of the
connector).
Devices utilizing the 'B' connector must be designed to work with worst case
maximum length detachable cable. Detachable cable assemblies may be used
only on full-speed devices. Note also that using a full-speed detachable cable
on a low-speed device may exceed the maximum low-speed cable length.
Finally, Figures 2.22 and 2.23, respectively show the pin connections for
connectors 'A' and 'B' whilst Figure 2.24 shows the pin assignment and
recommended colour coding.

Figure 2.23 USB connector
(type B)

Representative I/O
cards

The final part of this chapter describes some representative I/O interface cards

and bus connected devices. These details have been included in order to provide
readers with an insight into products that are currently available 'off-the-
shelf ' and that can be used for a wide variety of control, data acquisition and
instrumentation applications.

Measurement Computing Corporation PDISO-8

The Measurement Computing Corporation PDISO-8 is an inexpensive eight-
channel 500 V isolated input and 8-channel relay output interface card designed
for control and sensing applications. The interface card is intended for use with
a standard PCI bus and is Plug and Play compatible. Where necessary the input
range may be extended by adding an additional fixed resistor in series with the
existing 1.6 k input resistor.