Tektronix PFG 5105, Инструкция по эксплуатации

Страница: 70 / 89

Programming
MESSAGES AND COMMUNCIATION PROTOCOL
Command Separator
A message consists of one command or a series of
commands, followed by a message terminator. Com­
mands in multiple command messages must be sep­
arated by semicolons. A semicolon at the end of a
message is optional. For example, each lin.e below
is a message.
INIT
TEST?;INIT;RQS ON;USER OFF;ID?;SET?
TEST?;
Address and Message Terminator
Selection
Messages may be terminated with EOI or the ASCII
line feed (LF) character. Some controllers assert EOI
concurrently with the last data byte; others use only
the LF character as a terminator. T he instrument can
be set to accept either terminator. With EOI only
selected as the terminator, the instrument interprets
a data by t e received with EOI asserted, as the end
of the input message; it also asserts EOI concurrently
with the last by t e of the output messages. With the
LF/EOI setting, the instrument interprets the LF char­
acter without EOI asserted (or any data by t e received
with EOI asserted) as the end of an input message;
it transmits carriage return (CR) followed by line feed
(the LF with EOI asserted) to terminate output mes­
sages.
NOTE
Do not use LF mode when transmitting or
receiving Binary Block data. See SEND?, STOR.
T he PFG 5105/5505 is shipped from the factor y with
a GPIB address of 8; the terminator is LF with EOI.
Both the GPIB primary address and the message
terminator are selected using front panel keys. These
selections are stored in non-volatile RAM. T he follow­
ing steps outline the selection process:
1. Press the INST ID key. T he current GPIB address
and terminator are indicated in the display window
(while the key is pressed).
2. To change the GPIB address, press the SPCL key;
press keypad numbers 240; press ENTER.
Press the keypad numbers for the new GPIB
address; press ENTER. T he new address should
be shown in the display window.
PFG 5105/5505 Instruction Manual
T he legal values are
o
to 31. Using address 31
disconnects the PFG 5105/5505 from bus com­
munication.
3. To change the terminator selection, press the SPCL
key; press keypad numbers 241; press ENTER;
press the INCREMENT up- or down-arrow key to
change the terminator selection. T he new ter­
minator selection should be indicated in the display
window.
Formatting a Message
Commands sent to TM 5000 instruments must have
the proper format (syntax) to be understood; however,
this format is flexible in that many variations are
acceptable. T he following describes the format and
the acceptable variations.
T he instruments expect all commands to be encoded
in ASCII, with either upper or lower case ASCII
characters acceptable. All data output is in upper
case (see Fig. 3-3). As previously discussed, a com­
mand consists of a header, followed if necessary, by
arguments. A command with arguments must have
a header delimiter, which is the space character (SP)
bet w een the header and the argument. T he space
character (SP), carriage return (CR), and line feed
(LF) are shown as subscript in the following examples.
RQSspON
If extra formatting characters SP, CR, and LF (the LF
cannot be used for format in the LF/EOI terminator
mode) are added between the header delimiter and
the argument, those characters are ignored by the
instrument.
Example 1: RQSspON;
Example 2: RQSsp spON;
Example 3: RQSsp CR
LF
SP spON
In general, these formatting characters are ignored
after any delimiter and at the beginning and end of
a message. For example:
spRQSspONcR
LF
spUSERspOFF
In the command list, some headers and arguments
are listed in two forms, a full-length version and an
abbreviated version. T he instrument accepts any
header or argument containing at least the characters
listed in the short form; any characters added to the
3-25