B&R MAPPC800-ENG, User Manual

Page: 365 / 396

Appendix A • Glossary
Appen
dix
A
365 Panel PC 800 User's Manual V 1.00
CPU
An abbreviation for " C entral P rocessing U nit". Interprets and executes commands. It is also
known as a "microprocessor" or "processor" for short. A processor is able to receive, decode and
execute commands, as well as transfer information to and from other resources via the computer
bus.
CTS
An abbreviation for " C lear T o S end". A signal used when transferring serial data from modem to
computer, indicating its readiness to send the data. CTS is a hardware signal which is transferred
via line number 5 in compliance with the RS-232-C standard.
DCD
An abbreviation for " D ata C arrier D etected". A signal used in serial communication that is sent
by the modem to the computer it is connected to, indicating that it is ready for transfer.
Dial-up
Data is transferred over the telephone network using a modem or an ISDN adapter.
DIMM
"Double In-line Memory Module" consisting of one or more RAM chips on a small circuit board
that is connected with the motherboard of a computer.
DMA
D irect M emory A ccess > Accelerated direct access to a computer’s RAM by bypassing the CPU.
DRAM
An abbreviation for " D ynamic R andom A ccess M emory". Dynamic RAM consists of an
integrated semiconductor circuit that stores information based on the capacitor principle.
Capacitors lose their charge in a relatively short time. Therefore, dynamic RAM circuit boards
must contain a logic that allows continual recharging of RAM chips. Since the processor cannot
access dynamic RAM while it is being recharged, one or more waiting states can occur when
reading or writing data. Although it is slower, dynamic RAM is used more often than static RAM
since the simple design of the circuits means that it can store four times more data than static
RAM.
D