KEPCO TMA 4882-27 - Manual (Page 31)

TMA 4882-27 021910
3-5
Carriage Return (0D
H
) Causes the input buffer to be parsed by the TMA 4882-27 controller.
Line Feed (0A
H
) Causes the input buffer to be parsed by the TMA 4882-27controller.
> 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.
3.5.3 RS 232 IMPLEMENTATION
The following paragraphs are provided to help the user understand how the RS 232 serial inter-
face is implemented in the TMA 4882-27. 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 com-
mand originator (computer) and the TMA 4882-27 power supply controller, thus avoiding a more
complex “handshake” protocol.
When the TMA 4882-27 controller is in the RS 232 echo mode it returns all data sent to the host
controller. The TMA 4882-27 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 TMA 4882-27. As shown in Figure 3-1,
there are times when the TMA 4882-27 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
)