KEPCO ABC-DM SERIES - Manual (Page 49)

ABC 040104
3-17
3.6.3.3 XON XOFF METHOD
The XON XOFF method allows the ABC to control when the command originator is allowed to
send data. The command originator can only send data after the XON (transmission on) charac-
ter (011
H
) has been received; the command originator stops sending data after receiving the
XOFF (transmission off) character (013
H
), and waits until the XON character is received before
sending additional data.
Control characters, either CR or LF, are returned as XOFF CR if echo mode is on, and as XOFF
if echo mode is off. XOFF stops data from the command originator and the ABC returns the nor-
mal sequence of CR LF (if echo mode is enabled).
3.6.4 ISOLATING RS 232 COMMUNICATION PROBLEMS
A Loop Back test can be run from the front panel to aid in isolating RS 232 communication prob-
lems. The unit is designed to pass the test only with the Loop Back test connector (part of Kit
219-0436, see Table 1-4) installed.
1. With the power supply in local mode, command entry status , press MENU key until LCD
reads
LOOP BACK TEST UNTESTED 1=RUN
.
2. Press the 1 key to run the test with the Loop Back Test connector NOT installed and very the
LCD reads
FAILED
. If the LCD reads
PASSED
, the power supply is defective and requires
repair.
3. Install the loop back test connector into RS 232 port and press the 1 key to rerun the test. If
the LCD reads
PASSED
, the power supply is operating properly. If the LCD reads
FAILED
,
the unit requires repair.
4. To test the integrity of the cable assembly connecting the power supply RS 232 port to the
computer, remove the Loop Back test connector from the power supply RS 232 port and
connect the cable in its place. With the DB9 adapter installed on the opposite end of the
cable, connect a short jumper wire between pins 2 and 3 of the adapter connector and
repeat the test of (3) above. If the LCD display reads
FAILED
, the cord is either the improper
type (not null modem) or is defective. If the LCD display reads
PASSED
, the cable is correct;
remove the jumper and reconnect the cable to the computer.
If each of the above steps is completed successfully, the problem lies in the computer hard-
ware and/or software. Refer to the Product Support area of the Kepco website for additional
information regarding RS 232 communications problems: www.kepcopower.com/support.
3.7 SCPI PROGRAMMING
SCPI (Standard Commands for Programmable Instruments) is a programming language con-
forming to the protocols and standards established by IEEE 488.2 (reference document
ANSI/IEEE Std 488.2, IEEE Standard Codes, Formats, Protocols, and Common Commands). SCPI
commands are sent to the ABC Power Supply as ASCII output strings within the selected pro-
gramming language (PASCAL, BASIC, etc.) in accordance with the manufacturer’s require-
ments for the particular GPIB controller card used.
Different programming languages (e.g., BASIC, C, PASCAL, etc.) have different ways of repre-
senting data that is to be put on the RS 232 or IEEE 488 (GPIB) bus. It is up to the programmer
to determine how to output the character sequence required for the programming language
used. Address information (GPIB address) must be included before the command sequence.
(See PAR.3.5.2 to establish the ABC Power Supply GPIB address.)