4
Remote Operations Using the IEEE 488 Interface
Using the 8508A Reference Multimeter in a System
Data Element
,
Program Header
phs
adj201f.eps
Program Header Separator - phs
The Program Header
The ‘Program Header’ provides the main command identification. This may be followed
by ‘Program Data Elements’ and these must be separated from the ‘Program Header’ by
a ‘Program Header Separator’.
The Program Header Separator
The ‘Program Header Separator’ is one or more ‘white space’ characters excluding the
message terminator (NL).
Program Data Elements
Four versions of the defined program data elements are employed. They are emphasized
in the following syntax diagrams, taken from the commands available for the Multimeter:
TRG_SRCE
INT
phs
EXT
adj203f.eps
Character
BLOCK
phs
Nrf
adj204f.eps
Decimal Numeric
(Nrf can be expressed in any of the ways defined by the Standard document.)
SERIAL
"
12 chars
"
phs
'
12 chars
'
adj205f.eps
String
( The maximum size of the string is specified in the command detail.)
Arbitrary Block Data Elements
Both the "Definite" and "Indefinite" forms specified in the Standard document are used,
as shown in the Syntax diagram below. The user message must be limited to a maximum
of 63 bytes.
The Definite form can be fitted into an assembly of message units, but the Indefinite form
(lower path) has no exit to further message units. In this case the program message must
be terminated to inform the instrument that the block is complete.
4-7
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