Pin
Designations and
Signal
Descriptions
The
mechanical
specification of the RS-232-C requires
a
25-pin
connector
(called
a
DB-25).
Table
2
specifies the
pin assignments
and signal descriptions
as they apply to the Radio Shack
RS-232-C
Interface.
Pin Number
Abbreviation Description
1 PGND Protective
Ground
2
TD Transmit Data
3
RD Receive Data
4
RTS Request-to-Send
5
CTS Clear-to-Send
6
DSR
Data Set Ready
7
SGND Signal
Ground
8 CD
Carrier Detect
20
DTR Data Terminal
Ready
22
Rl
|
Ring
Indicator
TABLE
2.
PEN
DESIGNATIONS AND SIGNAL
DESCRIPTION
Protective Ground:
This must
be bonded to the chassis
or
equipment
frame. It may
also be
connected to Signal Ground.
Transmit Data: Direction-to
data communication
equipment. Signals
on this
circuit
are
generated
by
the
data
terminal
equipment for
transmission of data
to
remote equipment.
This signal should
be
held in the marking
condition during intervals between characters
and at all times when
no data is being transmitted.
Received Data: Direction-from
data communication equipment.
Signals on this
circuit are received from remote equipment which
transmits data
to the terminal. This
signal
should
be
held
in the
marking condition during intervals
between characters and at all
times when no
data is being received.
Request-to-send:
Direction-to data communication equipment.
This
signal is required
by
the terminal equipment
to
control
the
direction of data transmission
by
the
data
communication
equipment.
On one-way
or duplex channels, the "on" condition maintains the
data communication
equipment in the transmit mode. The "off"
condition
maintains the data communication equipment in the
non-transmit mode.
On a half
duplex
channel, the "on" condition maintains
the
data
communication equipment
in
the transmit mode
and inhibits the
receive mode.
The
"off" condition maintains the data communication
equipment in the receive mode.
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