5522A
Operators Manual
5-22
Table 5-2. RS-232 Interface Wiring
Mnemonic Description
CTS Clear to Send
DB-9 Type DB connector, 9 pins
DB-25 Type DB connector, 25 pins
DCD Data Carrier Detect
DCE Data Communications Equipment
DSR Data Set Ready
DTE Data Terminal Equipment
DTR Data Terminal Ready
GND Ground
RI Ring Indicator
RLSD Received Line Signal Detector
RTD Request to Send
RX Receive Line
TX Transmit Line
IEEE-488 Interface Overview
The IEEE-488 parallel interface sends commands as data and receives measurements and
messages as data. The maximum data exchange rate is 1 Mbyte, with a maximum
distance of 20 meters for the sum length of the connecting cables. A single cable should
not exceed 4 meters in length. Some commands are reserved for RS-232 serial operation
because these functions must be implemented as IEEE messages per the IEEE Standards.
For example, the command REMOTE could be sent as data over the IEEE-488 interface
to place the Calibrator into remote, but it is not because the IEEE Standards call for the
remote function to be sent to the device as the uniline message REN. This is also true for
several other commands and functions, as shown below, with their equivalent RS-232
emulation. A summary of IEEE-488 messages is shown in Table 5-3.
Table 5-3. RS-232 Emulation of IEEE-488 Messages
IEEE-488 Message RS-232 Equivalent
GTL LOCAL command
GTR REMOTE command
LLO LOCKOUT command
SDC, DCL ^C (<Cntl> C) character [clear the device]
GET ^T (<Cntl> T) character [execute a group trigger]
SPE, SPD ^P (<Cntl> P) character [print the serial poll string]
UNL, UNT (not emulated on RS-232)
The IEEE-488 interface is based on the IEEE Standards 488.1 and 488.2. For detailed
information, refer to the standards IEEE-488.1 and IEEE-488.2.
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