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90 Cards in this Set

  • Front
  • Back
Any device that can transmit or send data; for example, a computer.
Data Terminal Equipment (DTE)
Any device that communicates the data; for example, a
Data Communications Equipment (DCE)
function is to transfer command information by
using the appropriate control signals from the transmitting computer to the receiving device.
External Function (EF) data
function is to transfer status information by using the appropriate control signals from a transmitting device to the receiving computer.
External Interrupt (EI) data
A device that serves as a shared entry
point from a local area network into a larger information resource such as a mainframe computer.
Signals necessary for completing I/O operations.
function is to receive information using the appropriate control
signals from a transmitting device by the receiving
Input Data (ID)
function is to transfer information using the appropriate control signals from a transmitting computer to the receiving device.
Output Data (OD)
Procedure required to initiate and maintain operations.
Recommended Standard
defined as that end of a
channel that receives information frames.
The end of a channel that transmits information frames.
I/O processor controls what?
the transfer of information between the computer’s main memory and the external equipments.
Relieves the CPU of the necessity to perform the time consuming functions of
establishing, directing, and monitoring transfers with
external equipments.
Changes the input and output
control and data signal voltages to the voltage
requirements of the computer or external equipments.
The IOA is a completely passive unit and functions under the direct control of the what?
represent the alphabetic and numeric information exchanged.
Data words
Specify an action to be accomplished by an external equipment.
Control words
sent by the computer to an External equipment to specify the type of operation it is to
Function (command) control words
sent to the computer to specify that an error
or special condition exists in an external equipment or
the status of an external equipment.
External interrupt words
all bits of information represented by a byte or word are input or output simultaneously
all bits of information are input or output one at a time.
Heart of the I/O section is the?
input/output processor
provide control over IOC
single or dual channel operations.
Command instructions
are stored in memory by
the main CPU program before the I/O operation takes
Chaining Instructions
some computers have the
capability to select operating modes. These options are usually found with computers that have an?
The even numbered channel provides the control signals on
lower half or lower order data bits.
The odd numbered
channel provides the
upper half or upper order data bits only
specified address mode provides the external
devices with a means of specifying an absolute memory
location for storage (write) or retrieval (read) of
information on a word-by-word basis.
Externally specified address (ESA)
externally specified index mode is identical to regular
transfers (input, output, external interrupt, and external
function) except that the IOC requires the external
device to specify an index address in main memory.
Externally specified index (ESI)
permits communication between two CPUs. In this mode, each computer appears as a external device to the other. During operations, the
computer that is outputting the data is defined as the
sending computer. The computer that is receiving the
data from the sending computer is defined as the
receiving computer
Intercomputer channel (IC)
control the type and number of words or bytes that are to be transferred by the pending operation.
Buffer control words (BCWs)
specify the next memory address, within the
buffer, for a transfer to take place.
Buffer address pointers
specifies where in memory the
IOC can find the next chaining instruction.
Chain address pointers (CAPs)
Are used to store characters for comparison with received (input) data characters.
Monitor words
Contains a code that is used to remove specific characters from the serial transmission stream.
Suppress word
loads the input or output BCW and BAP in control memory for the channel specified and initiates the input or output transfers.
Is used to load or write data
into single control memory word locations.
Load/write control memory
Is used to write the contents of a specified control memory address into a memory address for CPU processing.
Store control memory
Is used to set or clear (zero) specified bits or bit groups in control memory or main memory locations or the channel status word.
set/clear flag
Enables or disables sync, monitor, and suppress
capabilities indifferent serial configurations.
sync/set suppress/set monitor
It is used to turn on or turn off specific serial charnel signals such as data terminal ready.
Set/clear discrete (command and chain)
performs a variety of single and multichannel functions. It can be used to master clear a single or all IOC channels, input or output. It is also used to enable or disable all, low priority, or a single interrupts.
Channel control
the peripheral devices are tied directly into the CPU communication bus (control bus, data bus, and so forth)
Direct CPU Interface
(also called accumulator based I/O)
CPU accesses the I/O device by placing appropriate addressing information on the bus.
the CPU must regularly check— or poll — each channel or port in turn to determine if it has information for input or is ready to accept data for output.
CPU executes the loop
instructions, it periodically (say 20 times a second)
checks the status code from the keyboard to see if a
character has been entered.
I/O wait loop
indicates whether there is a new character in the INBUF register
disadvantages with polled I/O is that it?
involves the CPU throughout the input/output process.
the I/O section itself is capable of accessing memory via the computer communication buses.
requires more complex hardware and software, but makes far more efficient use of the computer’s time and capacities.
gives the computer an
advantage-speed & allows information to be moved
quickly in and out of memory without the intervention
of the CPU.
direct memory access (DMA)
A DMA controller is usually placed between?
the external device and the computer’s bus
Serves as a buffer between
main memory and the external device.
data register
more than one peripheral device is connected to a single port/channel
Daisy Chaining
In this method, separate lines are used for the request
and acknowledge lines. The I/O controller assigns
priority to each external device, which can be fixed or
Independent Request Control
takes into account such things as the type of connectors to be used,
the number of pin connections in the connectors, and
the maximum cable lengths allowed.
mechanical portion
include the allowable line voltages and the representations for the various voltage levels.
interface specifies
such things as which signals-timing, control, data, or
ground leads—are to be carried by each pin in the
define how signals are to be exchanged and the environment necessary to input and output data.
procedural characteristics
when true, enables the USART for reading/writing
when true, indicates the microprocessor is placing data or control words on the data bus to the USART.
WRITE DATA (WD) signal
when true, indicates the microprocessor is ready to receive data or status words from the USART.
The READ DATA (RD) signal
identifies the write operation transfer as data or control words, or the read operation transfer as data or
status words.
The CONTROL/DATA (C/D) signal
is sent from the computer to the external device to notify the external device that the computer is ready to transmit
data when HIGH.
Data Set Ready (DSR)
is sent from the external device to the computer
to indicate that the external device is ready to receive
data when HIGH.
Data Terminal Ready (DTR)
is sent from the external device to the computer to indicate that the external device is ready (HIGH) or busy
Request to Send (RTS)
is sent from the computer to the external device as a reply to the RTS signal.
Clear to Send (CTS)
Input/output interface is probably one of the most versatile of formats because it is designed
to handle either parallel or serial formatted information,
depending on the type of computer and its I/O
External interrupt enable
Input data request
External interrupt request
Input data acknowledge
External function request
External function acknowledge
Output data request
Output data acknowledge
parallel data of up to 41,667 words per second on one
transfers parallel data of up to 250,000 words per second on one cable.
transfers parallel data
of up to 250,000 words per second on one cable.
asynchronously transfers serial data using a 10
megabits per second (Mb/s) clock rate over a single
coaxial cable.
asynchronously transfers serial data of up to 10-million
bits per second on single triaxial cable. Channel control is similar to NTDS parallel channels
transfers serial data up to one million bits per second
over a distance of 300 feet.
equates with the
functional and procedural portions of RS-232.
TYPE G (RS-449)
transfers parallel data of up to 500,000 words per
second on one cable.
used for the fiberoptic implementation of type
an 8-bit parallel, high-level interface.
High-level means that instead of a host computer asking
for data by specifying a track, cylinder, and sector
number, all it asks for is a logical sector number.
small computer system interface (SCSI)
serial format. It can be
used for asynchronous and synchronous serial transfers.
RS-232 (EIA RS-232 and MIL-STD 188)
used for work group solutions and
work station intensive networks. It transfers serial I/O
data. It has the ability to operate at a 4- or 16-megabits
per second rate of data communication
Token Ring (IEEE 802.5)
specification that describes a
method for computers and data systems to connect and
share cabling (i.e., PC’s and mainframes). It transfers
serial I/O data in a specific packet format standard is commonly referred to as
IEEE 802.3 (Ethernet DIX)