Chapter 6, COMPUTER OPERATION
6-8
while in the binary dump mode it needs to know exactly how many bytes to read,
since the data itself can contain null characters. Only by doing this can the program
be prevented from requesting more data from the socket than the lock-in has actually
sent.
6.5.06 Delimiters
Most response transmissions consist of one or two numbers (expressed as ASCII
text) followed by a response terminator. Where the response of the lock-in amplifier
consists of two numbers in succession, they are separated by a byte called a
delimiter. This delimiter can be one of several ASCII characters and is common to
all interfaces; it is set via the DD command 6.6 Command Format
The simple commands listed in section 6.7 have one of five forms:
CMDNAME terminator
CMDNAME n terminator
CMDNAME [n] terminator
CMDNAME [n
1
[n
2
]] terminator
CMDNAME n
1
[n
2
] terminator
where CMDNAME is an alphanumeric string that defines the command, and n, n
1
, n
2
are parameters separated by spaces. When n is not enclosed in square brackets it
must be supplied. [n] means that n is optional. [n
1
[n
2
]] means that n
1
is optional and
if present may optionally be followed by n
2
. Upper-case and lower-case characters
are equivalent. Terminator bytes are defined in section 6.3.09.
Where the command syntax includes optional parameters and the command is
sent without the optional parameters, the response consists of a transmission of
the present values of the parameter(s).
Any response transmission consists of one or more numbers followed by a response
terminator. Where the response consists of two or more numbers in succession, they
are separated by a delimiter (sections 6.3.09, 6.3.04, and 6.5.05).
Some commands have an optional floating point mode which is invoked by
appending a . (full stop) character to the end of the command and before the
parameters. This allows some parameters to be entered or read in floating point
format. The floating point output format is given below.
±1.234E±01
The number of digits between the decimal point and the exponent varies depending
on the number but is a minimum of one and a maximum of eight. The input format is
not as strict but if a decimal point is used there must be a digit before it. An exponent
is optional. The following are all legal commands for setting the oscillator frequency
to 100.1 Hz:-
OF. 100.1
OF. 1.001E2
OF. +1.001E+02
OF. 1001E-1
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