SP237AES View Datasheet(PDF) - Signal Processing Technologies
Part Name
Description
Manufacturer
SP237AES Datasheet PDF : 17 Pages
| |||
Data Terminal Ready (DTR)
This is the pin the computer uses to tell periph-
eral devices that it is on–line and ready to
communicate.
Data Set Ready (DSR)
Peripheral devices use this line to tell the com-
puter that they are on–line and ready to commu-
nicate. When the modem is turned on and has
completed its self–test routine (assuming it does
one), it will send a signal to the PC by asserting
this line.
Request To Send (RTS)
The computer activates this line to notify the
peripheral device that it is ready to send data. In
this example, the computer notifies the modem
that it is ready to send data to be transmitted by
the modem.
Clear To Send (CTS)
This is the line on which the peripheral device
tells the computer that it is ready to receive data
from the computer. If the modem was not ready,
i.e. it was performing a loop–back self–test, for
example, it would not assert this line. Once the
modem was ready to receive data from the PC,
it would assert this line. When it receives the
CTS signal from the modem, the PC knows that
a data transmission path has been established
between itself and the modem.
Transmitted Data (TD or TX)
This is the pin on which the computer sends the
actual data signal to be transmitted, i.e. a posi-
tive voltage (+3V to +15V) to represent a logic
“0”, and a negative voltage (–3V to –15V) to
represent a logic “1”. The PC would send the
data on this line to be transmitted by the modem.
Ring Indicator (RI)
This line is used by the peripheral device to tell
the computer that a remote device wants to start
communicating. The modem would activate the
RI line to tell the computer that the remote
modem was calling, i.e. the phone is ringing.
Data Carrier Detect (DCD)
This line is used by the modem to tell the
computer that it has completed a transmission
path with the remote modem, and to expect to
start receiving data at any time.
Received Data (RD or RX)
This is the pin on which the modem sends the
computer the incoming data signal, i.e. a posi-
tive voltage (+3V to +15V) to represent a logic
“0”, and a negative voltage (-3V to -15V) to
represent a logic “1”.
INTERFACE EXAMPLE – A PRINTER
ON THE IBM PC SERIAL PORT
The RS-232 standard defines 22 serial interface
signals. These signals consist of ground lines,
timing, data, control and test signals, plus a set of
signals rarely used for a second data channel.
Many of these signal lines are not used in typical
RS-232 applications; in fact, the IBM® PC serial
port is implemented using only nine pins.
For example, consider the case of a PC using this
nine pin port to communicate with a peripheral
device such as a printer. We see the following
activity on each of the RS-232 lines as the com-
puter and printer are activated and communicate.
Signal Ground (GND)
The Signal Ground pin acts as a reference for all the
other signals. This pin is simply maintained at a 0V
level to serve as a level to which all other signals
are referenced. Both the PC and the printer will
have this line connected to their respective internal
ground lines.
Data Terminal Ready (DTR)
This is the pin the computer uses to tell peripheral
devices that it is on–line and ready to communi-
Signal Ground
Data Set Ready
Clear To Send
Ready To Send
Transmitted Data
(To Be Printed)
7
R6
R5
D
4
D
2
SP231A/232A
Signal Ground
D
Data Set Ready
D
Clear To Send
R
Ready To Send
R
Received Data
(To Be Printed)
SP231A/232A
Computer
IBM Printer Port Interconnections
Printer
Date: 8/3/04
+ 5V Powered Multi-Channel RS-232 Drivers/Receivers
11
© Copyright 2004 Sipex Corporation
|
|
Share Link: 