Teledyne T703, T703U 8.4.11. RS-232 COMMUNICATIONS

General Troubleshooting & Service Teledyne API T703/T703U Calibrator Operation Manual
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8.4.11. RS-232 COMMUNICATIONS
8.4.11.1. General RS-232 Troubleshooting
Teledyne API calibrators use the RS-232 communications protocol to allow the
instrument to be connected to a variety of computer-based equipment. RS-232 has been
used for many years and as equipment has become more advanced, connections between
various types of hardware have become increasingly difficult. Generally, every
manufacturer observes the signal and timing requirements of the protocol very carefully.
Problems with RS-232 connections usually center around four general areas:
 Incorrect cabling and connectors. See Section 5.1.2 for connector and pin-out
information.
 The BAUD rate and protocol are incorrectly configured. See Section 5.1.3.
 If a modem is being used, additional configuration and wiring rules must be
observed. See Section 5.2
 Incorrect setting of the DTE – DCE Switch is set correctly. See Section 5.1.1.
 Verify that cable (03596) that connects the serial COM ports of the CPU to J12 of
the motherboard is properly seated
8.4.11.2. Troubleshooting Calibrator/Modem or Terminal Operation
These are the general steps for troubleshooting problems with a modem connected to a
Teledyne API calibrator.
 Check cables for proper connection to the modem, terminal or computer.
 Check to make sure the DTE-DCE is in the correct position as described in Section
5.1.1.
 Check to make sure the set up command is correct (See Section 5.2)
 Verify that the Ready to Send (RTS) signal is at logic high. The T703 sets pin 7
(RTS) to greater than 3 volts to enable modem transmission.
 Make sure the BAUD rate, word length, and stop bit settings between modem and
calibrator match, See Section 5.1.3.
 Use the RS-232 test function to send “w” characters to the modem, terminal or
computer; See Section 5.1.5
 Get your terminal, modem or computer to transmit data to the calibrator (holding
down the space bar is one way); the green LED should flicker as the instrument is
receiving data.
 Make sure that the communications software or terminal emulation software is
functioning properly.
NOTE
Further help with serial communications is available in a separate manual “RS-232 Programming Notes”
Teledyne API part number 013500000.
07223C DCN6572