KEPCO BHK-MG 200W (Full Rack) Series - Manual (Page 65)

BHK-MG (OPR) 022014
3-21
To change baud rate refer to PAR’s. B.73 and B.74. To select prompt refer to PAR’s. B.79 and
B.80. To select echo refer to PAR’s. B.75 and B.76. To select XON/XOFF, refer to PAR’s. B.77,
B.78.
3.4.1 SETTING RS 232 BAUD RATE
When the power supply is in local mode, command entry status , press MENU key until LCD
displays
BAUD RATE =
. The top line of the LCD indicates the current RS 232 baud rate (default
= 9600). Use and keys to scroll through the available baud rate settings (19200, 9600,
4800 or 2400). Press ENTER to accept new setting (new baud rate is effective immediately), or
CLEAR to exit without changing setting.
3.4.2 SERIAL INTERFACE
The serial interface behaves like the GPIB interface in that the command is parsed after receiv-
ing a control character of either a Line Feed or Carriage Return. The serial interface supports six
special control characters. The three special control characters are:
Backspace (08
H
) Causes the last character in the input buffer to be removed from the
input buffer queue.
Carriage Return (0D
H
) Causes the input buffer to be parsed by the BHK-MG.
Line Feed (0A
H
) Causes the input buffer to be parsed by the BHK-MG.
3.4.3 RS 232 IMPLEMENTATION
The following paragraphs are provided to help the user understand how the RS 232 serial inter-
face is implemented in the BHK-MG. Since the RS 232 protocol does not use a parity bit, the
echo mode is the default method used to ensure reliable communication between the command
originator (computer) and the BHK-MG power supply, thus avoiding a more complex “hand-
shake” protocol.
When the BHK-MG is in the RS 232 echo mode it returns all data sent to the host controller. The
BHK-MG provides two additional options that allow handshake communication: the Prompt
method and the XON XOFF method. In standard echo mode the controller must verify that each
character is echoed back by the BHK-MG. As shown in Figure 3-3, there are times when the
BHK-MG does not echo back the character from the controller, requiring that the controller
resend the character. By using the handshake options (prompt and XON XOFF) the host con-
troller can ensure that serial data interrupts occurring after parsing of the incoming message do
not result in lost data.
Figure 3-3 illustrates the default echo mode, the prompt method and the XON XOFF method
described in the following paragraphs.