Terminator; Flow Control (Signal Handshaking); Rs-232 Connections - Keithley 2500 User Manual

13-18 Remote Operations

Terminator

The Model 2500 can be configured to terminate each program message that it transmits to
the controller with any of the following combinations of <CR> and <LF>:
<CR>
<CR+LF>
<LF>
<LF+CR>

Flow control (signal handshaking)

Signal handshaking between the controller and the instrument lets the two devices com-
municate with each other about readiness to receive data. The Model 2500 does not sup-
port hardware handshaking (flow control).
Software flow control is in the form of XON and XOFF characters and is enabled when
XON-XOFF is selected from the RS-232 FLOW CONTROL menu. When the input queue
of the unit becomes more than 3/4 full, the instrument issues an XOFF command. The
control program should respond to this and stop sending characters until the Model 2500
issues the XON, which it will do once its input buffer has dropped below half-full. The
Model 2500 recognizes XON and XOFF sent from the controller. An XOFF will cause the
instrument to stop outputting characters until it sees an XON. Incoming commands are
processed after the <CR> character is received from the controller.
If NONE is the selected flow control, there will be no signal handshaking between the
controller and the Model 2500. Data will be lost if transmitted before the receiving device
is ready.

RS-232 connections

The RS-232 serial port
straight-through RS-232 cable terminated with DB-9 connectors. Do not use a null modem
cable. The serial port uses the transmit (TXD), receive (RXD), and signal ground (GND)
lines of the RS-232 standard.
interface, and
If your computer uses a DB-25 connector for the RS-232 interface, you will need a cable
or adapter with a DB-25 connector on one end and a DB-9 connector on the other, wired
straight through (not null modem).
Figure 13-4
RS-232 interface connector
Rear Panel Connector
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
TestEquipmentDepot.com
Carriage return
Carriage return and line feed
Line feed
Line feed and carriage return
(Figure
Figure 13-4
Table 13-2 shows the pinout for the connector.
RS-232
5 4 3 2 1
9 8 7 6
Models 2500 and 2502 User's Manual
13-3) is connected to the serial port of a computer using a
shows the rear panel connector for the RS-232