KEPCO MST 488 Programmer - Manual (Page 30)

3-4
MST488-27 013004
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 MST 488-27 controller.
Line Feed (0A
H
) Causes the input buffer to be parsed by the MST 488-27controller.
> and < The > character turns on the echo mode upon receipt of the character.
The < character turns off the echo mode. The message “echo off“ or
“echo on“ will be displayed to confirm this.
3.3.3 RS 232 IMPLEMENTATION
The following paragraphs are provided to help the user understand how the RS 232 serial inter-
face is implemented in the MST 488-27. 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 MST 488-27 power supply controller, thus avoiding a more com-
plex “handshake” protocol.
When the MST 488-27 controller is in the RS 232 echo mode it returns all data sent to the host
controller. The MST 488-27 provides two additional options that allow handshake communica-
tion: the Prompt method and the XON XOFF method. In standard echo mode the controller
must verify that each character is echoed back by the MST 488-27. As shown in Figure 3-1,
there are times when the MST 488-27 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 controller can ensure that serial data interrupts occurring after parsing of
the incoming message do not result in lost data.
Figure 3-1 illustrates the default echo mode, the prompt method and the XON XOFF method
described in the following paragraphs.
FIGURE 3-1. RS 232 IMPLEMENTATION
Only four control characters (characters between 00
H
and 1F
H
) are acknowledged by the power
supply:
• Carriage Return (CR, 0D
H
)
• Line Feed (LF, 0A
H
)
• Back Space (BS, 08
H
)
• Escape (ESC, 01B
H
)