Input/Output Interfaces

5.6.1 USB Connector

These systems provide type-A USB ports as shown in Figure 5-7.

1 2 3 4

Figure 5-7. Universal Serial Bus Connector (as viewed from rear of chassis)

 

 

 

Table 5-6.

 

 

 

USB Connector Pinout

 

 

 

 

 

 

 

 

Pin

Signal

Description

 

Pin

Signal

Description

 

 

 

 

 

 

 

1

Vcc

+5 VDC

 

3

USB+

Data (plus)

 

 

 

 

 

 

 

2

USB-

Data (minus)

 

4

GND

Ground

 

 

 

 

 

 

 

5.6.2 USB Cable Data

The recommended cable length between the host and the USB device should be no longer than sixteen feet for full-channel (12 MB/s) operation, depending on cable specification (see following table).

Table 5-7.

USB Cable Length Data

Conductor Size

Resistance

Maximum Length

 

 

 

20 AWG

0.036 Ω

16.4 ft (5.00 m)

 

 

 

22 AWG

0.057 Ω

9.94 ft (3.03 m)

 

 

 

24 AWG

0.091 Ω

6.82 ft (2.08 m)

 

 

 

26 AWG

0.145 Ω

4.30 ft (1.31 m)

 

 

 

28 AWG

0.232 Ω

2.66 ft (0.81 m)

NOTE: For sub-channel (1.5 MB/s) operation and/or when using sub-standard cable shorter lengths may be allowable and/or necessary.

The shield, chassis ground, and power ground should be tied together at the host end but left unconnected at the device end to avoid ground loops.

Table 5-8.

USB Color Code

Signal

Insulation color

Signal

Insulation Color

 

 

 

 

Data +

Green

Vcc

Red

 

 

 

 

Data -

White

Ground

Black

 

 

 

 

5-10

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Technical Reference Guide