KEPCO TMA 4882-27 - Manual (Page 32)

3-6
TMA 4882-27 021910
BS deletes the last character entered, with the exception of CR or LF characters. Either the CR
or LF character acts as the line terminator, initiating parsing of the ASCII data sent to the TMA
4882-27 by the command originator. When the line is parsed and the commands are sent to the
individual power supplies via the IEEE 1118 bus, the TMA 4882-27 sends the line terminator
sequence CR LF to the command originator.
The ESC character is used for synchronization, causing the TMA 4882-27 to reset its input buf-
fer and return a CR LF sequence.
All non-control characters are sent via the serial port of the command originator. The control
character BS is echoed as BS Space BS. Only the first control character is returned in response
to either a CR LF or LF CR character sequence (see Figure 3-1).
3.5.3.1 ECHO MODE
Echo mode is the default method of ensuring data is transferred without errors. Each byte (char-
acter) is echoed back to the sender where it is verified as the same character that was just sent.
If the character is incorrect or missing, the sender sends the character again until the correct
character is verified as having been received.
All non-control characters are sent via the serial port of the command originator. The control
character BS is echoed as BS Space BS. Only the first control character is returned in response
to either a CR LF or LF CR character sequence (see Figure 3-1).
3.5.3.2 PROMPT METHOD
The command originator sends a message line (command) to the TMA 4882-27 and waits until
the prompt sequence CR LF > (3E
H
, 62
10
) is received. The TMA 4882-27 sends the prompt
sequence CR LF > to the command originator indicating the power supply is ready to receive
the next command 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 TMA 4882-27 is identical for echo mode and prompt mode; implementation of prompt
mode is at the command originator.
3.5.3.3 XON XOFF METHOD
The XON XOFF method allows the TMA 4882-27 to control when the command originator is
allowed to send data. The command originator can only send data after the XON (transmission
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. The XON XOFF method can be implemented indepen-
dently of the echo method using the special commands described below (PAR 3.5.3.4).