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If you are having trouble with RS 232 communication using MST 488-27, MBT G option or TMA 4882-27, the following are some common problems and their solution

Power Supply/Computer Interface Problems

The following steps are suggested as a means of troubleshooting common problems associated with RS 232 communications. These steps are intended as a guideline only, and should not be interpreted as a complete listing of possible problems or solutions to RS 232 communications problems

1. Verify the operation the power supply's RS 232 port using the specific test procedure called out in the power supply Operator's Manual.

2. Check the cable type used for interconnecting the power supply and computer RS 232 ports. The cable must be a null modem type, which deliberately cross-wires the transmit and receive wires. If an extension-type patch cord is used, a null modem adapter must be employed to achieve this function. A simple way to test for the correct cable type is to connect the desired cable assembly to the power supply's RS 232 port and terminate it with a loopback connection similar to that used for verifying the power supply port - a simple jumper connecting the transmit and receive pins will suffice. Repeating the power supply's port verification, or loopback, test will produce passing results for the proper cable configuration. A test failure indicates either a defective cable or improper cable type, i.e. not null modem.

3. If the above tests are successfully conmpleted but RS 232 programming problems persist, the problem may be related to configuration mismatch of the computer and power supply ports. Check that the baud rate setting for each port is identical, that parity is set to OFF and number of bits per character is set to 8.

4. If the settings are correct, set the power supply and computer as follows: 9600 baud rate, parity to OFF, character bits to 8. Rerun the loopback test while monitoring communications with the computer: the results should display manufacturer name, power supply model, serial number, and firmware revision, simlar to the following KEPCO, ABC 10-10DM, A12345, 3.10.

5. If the data returned in (step 4.) above is incorrect, disconnect the RS 232 cable from the computer and either a) install the loopback test connector used for power supply port verification in its place, or b) install the transmit-receive jumper described in (step 2.) above. Send a data string to the RS 232 port and verify that the data is returned to the computer. If the data is not returned, the computer hardware is probably at fault.

6. If the data returned in (step 5.) above is correct, send the *IDN? query to the power supply: the communications program should return the same data as in (step 4.) above. If no data is returned, recheck communications setup as indicated in (step 4.) above, and verify that the program is transmitting the line feed character.

Unit Not Working at 4800 Baud When Using Serial Communication

Answer: The RS-232 port of the Kepco MST 488-27, MBT G option and TMA 488-27 controllers allows the user to change the baud rate at power up by adding a jumper between the CTS and RTS pins 7 and 8 on the Kepco controller side of the cable. Therefore, there should be no interconnections between pins 7 and 8 on the cable being used to operate the Kepco controller.

Losing Characters When using Serial communication

Answer: If using only serial communication on the TMA 488-27, MBT G option or the MST 488-27 controllers, connect pins 7 and 8 on the serial port and then set the DIP switches to establish the baudrate, XON-XOff state and echo state. Enabling XOn XOff on the controller and the sending computer system will correct the problem. Our newer controllers like the KLP and High power BOP default to XON-XOFF enabled.



KEPCO, INC. 131-38 SANFORD AVENUE FLUSHING, NY. 11355 U.S.A.
TEL (718) 461-7000 FAX (718) 767-1102
www.kepcopower.com email: hq@kepcopower.com