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PDF RS232 Data sheet ( Hoja de datos )
| Número de pieza | RS232 | |
| Descripción | The RS-232 Standard | |
| Fabricantes | ETC | |
| Logotipo |  |
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 1. PDF Datasheet - Communications Interface  Hay una vista previa y un enlace de descarga de RS232 (archivo pdf) en la parte inferior de esta página. Total 2 Páginas | ||
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The RS-232 Standard
Information being transferred
between data processing equipment
and peripherals is in the form of
digital data which is transmitted in
either a serial or parallel mode.
Parallel communications are used
mainly for connections between
test instruments or computers and
printers, while serial is often used
between computers and other
peripherals.
Serial transmission involves the
sending of data one bit at a time,
over a single communications line.
In contrast, parallel communications
require at least as many lines as
there are bits in a word being
transmitted (for an 8-bit word, a
minimum of 8 lines are needed).
Serial transmission is beneficial
for long distance communications,
whereas parallel is designed for
short distances or when very high
transmission rates are required.
Standards
One of the advantages of a serial
system is that it lends itself to
transmission over telephone lines.
The serial digital data can be
converted by modem, placed onto
a standard voice-grade telephone
line, and converted back to serial
digital data at the receiving end of
the line by another modem.
Officially, RS-232 is defined as the
“Interface between data terminal
equipment and data
communications equipment using
serial binary data exchange.” This
definition defines data terminal
equipment (DTE) as the computer,
while data communications
equipment (DCE) is the modem.
A modem cable has pin-to-pin
connections, and is designed to
connect a DTE device to a DCE
device.
Interfaces
Selecting a Cable
In addition to communications
The major consideration in choosing
between computer equipment over an RS-232 cable is, what devices
telephone lines, RS-232 is now
are to be connected? First, are you
widely used for direct connections connecting two DTE devices (null
between data acquisition devices
modem cable) or a DTE device to
and computer systems. As in the
a DCE device (modem cable)?
definition of RS-232, the computer Second, what connectors are
is data transmission equipment
required on each end, male or
(DTE). However, many interface
female, 25-pin or 9-pin (AT style)?
products are not data
Usually, it is recommended that the
communications equipment (DCE). user obtain the two devices to be
Null modem cables are designed for connected, and then determine
this situation; rather than having the which cable is required.
pin- to-pin connections of modem
cables, null modem cables have
different internal wiring to allow DTE RS-232 Specifications
devices to communicate with one
another.
Cabling Options
RS-232 cables are commonly
available with either 4, 9 or 25-pin
wiring. The 25-pin cable connects
TRANSMITTED SIGNAL
VOLTAGE LEVELS:
Binary 0: +5 to +15 Vdc
(called a “space” or “on”)
Binary 1: -5 to -15 Vdc
(called a “mark” or “off”)
every pin; the 9-pin cables do not
include many of the uncommonly
RECEIVED SIGNAL
VOLTAGE LEVELS:
used connections; 4-pin cables
provide the bare minimum
Binary 0: +3 to +13 Vdc
Binary 1: -3 to -13 Vdc
connections, and have jumpers
to provide “handshaking” for those
devices that require it. These
jumpers connect pins 4, 5 and 8,
DATA FORMAT:
Start bit: Binary 0
Data: 5, 6, 7 or 8 bits
Parity: Odd, even, mark or space
and also pins 6 and 20.
(not used with 8-bit data)
Stop bit: Binary 1,
The advent of the IBM PC AT has
one or two bits
created a new wrinkle in RS-232
communications. Rather than
having the standard 25-pin
Transmission Example
connector, this computer and many
new expansion boards for PC’s
111110110000101111
feature a 9-pin serial port. To
connect this port to a standard 25-
pin port, a 9-to-25-pin adaptor cable
can be utilized, or the user can
create his own cable specifically
TRAILING IDLE
BITS
STOP BIT
PARITY BIT
CHARACTER
"A"
Data Flow
LEADING
IDLE BITS
START BIT
for that purpose.
Pin Assignments 25-Pin Style
9-Pin "AT" Style
PIN NUMBER
PIN
NUMBER
PIN NUMBER
1 DATA CARRIER DETECT
SECONDARY TRANSMITTED DATA 14
DATA SET READY 6
2 RECEIVED DATA
DCE TRANSMITTER SIGNAL ELEMENT TIMING 15
SECONDARY RECEIVED DATA 16
RECEIVER SIGNAL ELEMENT TIMING 17
REQUEST TO SEND 7
3 TRANSMITTED DATA
18
SECONDARY REQUEST TO SEND 19
DATA TERMINAL READY 20
CLEAR TO SEND 8
4 DATA TERMINAL READY
SIGNAL QUALITY DETECTOR 21
RING INDICATOR 22
DATA SIGNAL RATE SELECTOR 23
RING INDICATOR 9
5 SIGNAL GROUND
DTE TRANSMITTER SIGNAL ELEMENT TIMING 24
25
PIN
NUMBER
1 PROTECTIVE GROUND
2 TRANSMITTED DATA
3 RECEIVED DATA
4 REQUEST TO SEND
5 CLEAR TO SEND
6 DATA SET READY
7 SIGNAL GROUND/COMMON RETURN
8 RECEIVED LINE SIGNAL DETECTOR
9 +VOLTAGE
10 - VOLTAGE
11
12 SECONDARY RECEIVED LINE SIGNAL DETECTOR
13 SECONDARY CLEAR TO SEND
Z-10
ZZ
1 page | ||
| Páginas | Total 2 Páginas | |
| PDF Descargar | [ Datasheet RS232.PDF ] | |
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