Chapter 1: General Overview
1-7
101-Key style keyboard
The foundational difference between the NCR PS/2 keyboard and the
NCR USB keyboard is the communications between the keyboard and
the host computer. The PS/2 keyboard communicates using the PS/2
communications protocol, which is bit-serial and operates at
approximately 25 Kb. The USB keyboard uses the USB 1.1 protocol,
which is a different bit-serial protocol that operates at either 1.5 or 12
Mb. NCR’s keyboard operates at 12 Mb except for the Glide Pad, which
operates at 1.5 Mb.
Furthermore, each of these protocols includes a software layer. The
PS/2 software layer is very simplistic, and presents a challenge when
adding additional capabilities beyond the keyboard itself. All the
added devices, such as MSR, Keylock, tone, and scanner are
implemented as
wedge
devices. This means that these devices are
wedged
into the keyboard data stream and must spoof their way past
the operating system to transfer data. This technique, though
widespread, is burdened with problems, and is not standardized,
resulting in installation and support difficulties.
The USB software layer is standardized and well defined. It supports
multiple simultaneous channels of communications, and permits
additional capabilities to be added without negative impact.
Furthermore, USB defines several levels of standards, including a
standard for Human Interface Devices. This standard specifies
behavior for many devices that are widely used in the computer
industry, and permits proprietary extensions to be added for those
devices that are less widely used. NCR’s USB keyboard includes both
fully standard HID devices, such as the keyboard itself, the Glide Pad,
and the MSR, and less-widely used and thus customized HID devices
such as the Keylock and Error Tone.
The USB keyboard implements a standard USB Hub internally. This
hub provides independent connectivity to the several functional
sections that comprise the keyboard.
Summary of Contents for 5932
Page 1: ...NCR 5932 USB Keyboard User s Guide B005 0000 1395 Issue C...
Page 4: ...iv...
Page 40: ......
Page 58: ......
