KEPCO MBT Series - Manual (Page 93)

MBTSVC111609
3-55
mand and data will not be lost. The prompt method is similar to the echo method described
above, except that the command originator does not have to compare each character and
repeat any characters dropped while the IEEE 1118 bus (BITBUS) is active. The operation of
the MBT-G is identical for echo mode and prompt mode; implementation of prompt mode is at
the command originator.
3.3.3.4 XON XOFF METHOD
The XON XOFF method allows the MBT-G 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. The XON XOFF method can be implemented independently of the
echo method using the special commands described below (PAR 3.3.3.5).
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 MBT-G returns the
normal sequence of CR LF (if echo mode is enabled).
3.3.3.5 SPECIAL COMMANDS
The serial parser supports the command RSMODE to allow quick changes to RS 232 protocol.
RSMODEn This command is used to implement the XON XOFF method and control whether
echo mode is on or off. The RSMODE sequence is followed by a number n: 0,
through 5, defined in Table 3-23. This command must be the first command on a
line.
3.3.4 PROGRAMMING TECHNIQUES TO OPTIMIZE POWER SUPPLY PERFORMANCE
Kepco's auto-crossover digital supplies can operate in either voltage mode with current limit, or
current mode with voltage limit. The operating mode is determined by the voltage and current
commands received, as well as the load. Each time voltage and current commands are
received, the unit must evaluate the commands and the load conditions to determine the proper
operating mode. Reducing the number of times this evaluation must be made is desirable
because Kepco's digital auto-crossover supplies employ two separate feedback loops. Each
time there is a potential mode change, there is always an uncontrolled period of a few millisec-
onds while the two feedback loops compete for control of the output. By changing only the
active parameter (e.g., voltage for voltage mode), there is no doubt as to what the operating
mode will be, so the unit is never uncontrolled, response is quick and no transients are possible.
Recommended programming techniques are:
TABLE 3-23. XON XOFF CONTROL
VALUE OF n ECHO PROMPT XON XOFF
0 OFF OFF DISABLED
1 ON ON DISABLED
2 OFF ON DISABLED
3 OFF OFF ENABLED
4 ON ON ENABLED
5 OFF ON ENABLED