KEPCO KLP Series (older -1200 models) Operator Manual - Manual (Page 57)

KLP073008
3-17
3.4.2.3 XON XOFF METHOD
The XON XOFF method allows the KLP Power Supply to control when the command originator
is allowed to send data. The command originator can only send data after the XON (transmis-
sion on) character (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 KLP returns the nor-
mal sequence of CR LF (if echo mode is enabled).
3.4.2.4 ISOLATING RS 232 COMMUNICATIONS PROBLEMS
A Loop Back test can be run from the KLP front panel to aid in isolating RS 232 communications
problems.
1. With the power supply in local mode, if the status display shows SET, tap either the CUR-
RENT or VOLTAGE controls to take the unit out of setpoint mode (status display goes from
SET to blank)
2. Use a thin tool (e.g., a paper clip), to press the FUNCTION switch repeatedly until the status
display shows UTIL. Press the DC OUTPUT switch to enter the Utilities menu. Rotate either
the VOLTAGE or CURRENT control until the status display shows LBT (Loop Back Test). At
this point the VOLTS display will show ----.
3. With the power supply's RS 232 port open (no connections), press the DC OUTPUT switch
once to run the test. The VOLTS display should show FAIL; if it reads PASS, the power sup-
ply is defective and requires repair.
4. Install the loop-back test connector (195-0112, see Table 1-4) at the RS 232 port, located on
the rear panel of the power supply (J3, Figure 2-2). (If the loop back test connector is not
available, install a jumper from pin 2 to pin 3 of the RS 232 port connector.) Press the DC
OUTPUT switch once to rerun the test. The VOLTS display should now read PASS; if it reads
FAIL, the power supply is defective and requires repair.
5. To test the integrity of the cable assembly connecting the power supply RS 232 port to the
computer, remove the loop back test connector or jumper and connect the cable in its place.
Install a jumper wire from pin 2 to pin 3 at the opposite end of the cable and repeat the test of
(step 4) above. If the VOLTS display reads FAIL, the cable is either the improper type (not
null modem) or defective. If the VOLTS display reads PASS, the cable is correct. Remove the
jumper and reconnect the cable to the computer.
6. To exit the utilities menu, press the FUNCTION switch repeatedly until the status display is
blank.
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.
3.5 IEEE 488 (GPIB) BUS PROTOCOL
Table 3-2 defines the interface capabilities of the KLP power supply (Talker/Listener) relative to
the IEEE 488 (GPIB) bus (reference document ANSI/IEEE Std 488: IEEE Standard Digital Interface
for Programmable Instrumentation) communicating with a Host Computer—Controller (Talker/Lis-