Sel SEL-DTA2, Инструкция по эксплуатации

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3.3
Date Code 20020329
SEL-DTA2 Instruction Manual
Communications
Communications Protocol
Communications Protocol
The communications protocol consists of hardware and software attributes.
Hardware protocol includes the control line functions described above. The
following software protocol is designed for manual and automatic
communications.
1. All commands received by the SEL-DTA2 must be of the form:
<command><ENTER> or <command><CR><LF>
Thus, a command transmitted to the SEL-DTA2 should consist
of the command followed by a carriage return or carriage return
and line feed. You may truncate commands to the first three
characters. Upper- and lowercase characters may be used
without distinction, except in passwords.
2. The SEL-DTA2 transmits all messages in the following format:
<MESSAGE LINE 1><CR><LF>
<MESSAGE LINE 2><CR><LF>
•
•
•
<LAST MESSAGE LINE><CR><LF>
Each line of the message ends with a carriage return and line
feed.
3. The SEL-DTA2 indicates the volume of data in its received-
data buffer through an XON/XOFF protocol.
When the buffer drops below ¼ full, the SEL-DTA2 transmits
XON (ASCII hex 11) and asserts the RTS output.
The SEL-DTA2 transmits XOFF (ASCII hex 13) when the
buffer fills over ¾ full. It deasserts the RTS output when the
buffer is 95% full. Transmission sources should monitor for the
XOFF character so they do not overwrite the input buffer.
Transmission should terminate at the end of the message in
progress when the transmission source receives XOFF and may
resume when the SEL-DTA2 sends XON.
4. An XON/XOFF procedure can be used to control the
SEL-DTA2 during data transmission. When the instrument
receives XOFF during transmission, it pauses until it receives
an XON. If there is no message in progress when the
SEL-DTA2 receives XOFF, it blocks transmission of any
message presented to its buffer. Messages are accepted after
XON is received.
The CAN character (ASCII hex 18) cancels a pending
transmission. This is useful in terminating an unwanted
transmission.
5. Control characters can be sent from most keyboards with the
following keystrokes:
XON : <CTRL>Q (hold down the Control key and press Q )
XOFF : <CTRL>S (hold down the Control key and press S )
CAN : <CTRL>X (hold down the Control key and press X )