4-11-1. Functional Element Summary
<Response Message> Represents a sequence
of one or more <Response Message Unit> elements
separated by <Response Message Unit Terminator>
elements.
<Response Message Unit> Represents a single
message unit sent from the device.
<Response Data> Represents any of the eleven
different <Response Data> types.
<Response Message Unit Separator> Separates
<Response Message Unit> elements from one an-
other in a <Response Message>.
<Response Data Separator> Separates sequen-
tial <Response Data> elements that are related to
the same header or to each other.
<Response Header Separator> Separates the
header from the associated <Response Data>.
<Response Message Terminator> Terminates a
<Response Message>.
<Response Header> Specifies the function of
the associated <Response Data> element(s). Alpha
characters mnemonically indicate the function.
<Character Response Data> A data type suitable
for sending short mnemonic character strings. Gen-
erally used when a numeric data type is not suitable.
<Decimal Numeric Response Data> A data type
response suitable for sending decimal integers or
decimal fractions with or without exponents.
<NonDecimal Numeric Response Data> A data
type suitable for sending integer numeric repre-
sentation in base 16, 8, or 2. Useful for data that
is more easily interpreted when directly expressed
in a non-decimal format.
<String Response Data> A data type suitable
for sending 7-bit ASCII character strings where the
content needs to be “Hidden” (by delimiters). This
element is generally used to send data for direct
display on a device.
<Definite Length Arbitrary Block Response
Data> A data type suitable for sending blocks of
arbitrary 8-bit information when the length is known
beforehand.
<Indefinite Length Arbitrary Block Response
Data> A data type suitable for sending blocks of
arbitrary 8-bit information when the length is not
known beforehand or when computing the length
beforehand is undesirable.
<Arbitrary ASCII Response data> A data type
suitable for sending arbitrary ASCII data bytes when
alternate data types are unworkable.
4-11-2. Separator Functional Element Summary
The various elements within the <Response Mes-
sage> are separated by ASCII characters that were
specially assigned for this purpose. These separators
are discussed in the following paragraphs.
4-11-2-1. Response Message Unit Separator
The <Response Message Unit Separator> separates
sequential <Response Message Unit> elements from
one another when multiple <Response Message Unit>
elements are sent in a <Response Message>. The
<Response Message Unit Separator> is defined as:
;
4-11-2-2. Response Data Separator
The <Response Data Separator> separates sequential
<Response Data> elements from one another when
multiple data elements are sent. The <Response
Data Separator> is defined as:
,
4-11-2-3. Response Header Separator
The <Response Header Separator> separates the
<Response Header> from the <Response Data>.
The <Response Header Separator> is defined as:
<Space>
4-11-3. Response Message Terminator
The <Response Message Terminator> element’s func-
tion is to terminate a sequence of one or more
<Response Message Unit> elements. There are three
possible <Response Message Terminator> elements:
1. NL (new line);
2. NL END (EOI); and
3. END (EOI)
NL is defined as a single ASCII-encoded byte
0A (10 decimal). Leading <White Space> elements
are not permitted. The instrument interprets any and
all of the three terminators as semantically equivalent.
No alternative encoding are allowed. Note that IEEE-
P981 amendment forbids the use of CR as a <Re-
sponse Message Terminator> element. This is be-
cause some controller treat CR as the end of
transmission and leave the LF character in the unit,
thereby creating an error in the controller.
Model 8020 IEEE-488.2 Operation
Page 4-19
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