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FTB-2 и FTB-2 Pro. Руководство пользователя - часть 24

B Data Types

The following section provides an overview of the most common data

types that may appear in EXFO’s documentation on commands and

queries. The information is supplied for guidance only.

For more detailed information, please refer to IEEE 488.2 and SCPI

standards.

Data types are divided into two groups: <PROGRAM DATA> for the types

that are used when you want to send messages to a device and

<RESPONSE DATA> for the types that are used when a device sends

responses to the controller.

The data types are presented in graphics often referred to as “railroad

diagrams”. The following example illustrates how to interpret such

diagrams.

The splitting arrow indicates a

choice of items

<Upper/lower

case alpha>

<Upper/lower

Entry

Exit

case alpha>

_

<digit>

In boxes: syntactic

The reverse arrow indicates that

In circles: literal

items (use the

the item specified in the box can

items (to be

elements to which

be repeated several times

typed as such)

they refer)

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Data Types

Applicable Data Types for Input—IEEE 488.2

Applicable Data Types for Input—IEEE 488.2

 <PROGRAM MESSAGE TERMINATOR>

END^

<wsp>

NL

END^

NL

In the diagram above,

 “NL” corresponds to ASCII character code 10, in decimal (0A in

binary)

 “END^” corresponds to the last data byte of the message sent with

EOI = True and ATN = False

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Data Types

Applicable Data Types for Input—IEEE 488.2

 <CHARACTER PROGRAM DATA>

This data type will be used to send short mnemonics when a

<DECIMAL NUMERIC PROGRAM DATA> cannot be used.

Examples: TRIANGLEWAVE, NCONTINUOUS

 <DECIMAL NUMERIC PROGRAM DATA> (or <NRf>)

This data type includes <NR1>, <NR2> and <NR3> data types. It will

be used for decimal fractions with or without an exponent. Instruments

will adapt the values they receive to fit their degree of precision. For

example, if an instrument has a precision of two digits after the

decimal point and the incoming value is 12.048, this value will be

rounded off to 12.05.

<mantissa>

<wsp>

<exponent>

The second diagram below illustrates the <mantissa> syntax.

+

<digit>

<digit>

-

<digit>

<digit>

The third diagram illustrates the <exponent> syntax.

+

E/e

<wsp>

<digit>

-

Examples: +2.0 e5, -.56E+4, 6.5e-10

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Data Types

Applicable Data Types for Input—IEEE 488.2

 <NON-DECIMAL NUMERIC PROGRAM DATA>

This data type will be used for integer representation in hexadecimal

(base 16), octal (base 8) or binary (base 2). The numeric

representations will begin with “#H” for hexadecimal, “#Q” for octal

and “#B” for binary.

A/a

B/b

#

H/h

C/c

D/d

E/e

F/f

<digit>

Examples: #Hf3bc015d, #h01a4, #hfe

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Data Types

Applicable Data Types for Input—IEEE 488.2

0

1

2

#

Q/q

3

4

5

6

7

Examples: #Q1234567, #q1275, #q07

0

#

B/b

1

Examples: #B10010111, #b10110, #b1100

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Data Types

Applicable Data Types for Input—IEEE 488.2

 <STRING PROGRAM DATA>

This data type will be used for strings containing 7-bit ASCII characters

that have to be enclosed in either single- or double-quotes delimiters.

If a string needs to contain a character that is exactly the same as the

delimiter, make sure to double the character to avoid syntax errors.

'

<inserted '>

'

'

<non single

quote char>

"

<inserted ">

"

"

<non single

quote char>

Examples: "SCPI Commands", ’SCPI Commands’, "SCPI ’Commands’",

’SCPI "Commands"’, "SCPI ""Commands""", ’SCPI ’’Commands’’’

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Data Types

Applicable Data Types for Input—IEEE 488.2

 <ARBITRARY BLOCK PROGRAM DATA>

This data type is used to send blocks of arbitrary 8-bit information

when you need to work with large amounts of data.

The actual length of the data that you send has the following structure:

 The first byte contains the # character.

 The byte that immediately follows contains the number of

subsequent bytes that you have to check to obtain the total length.

Note:

If you use a zero as the first digit (#0), it has to be followed by a

<PROGRAM MESSAGE TERMINATOR > so that the device will detect the

end of the <ARBITRARY BLOCK PROGRAM DATA>. This will also force

immediate termination of the message.

For example, if you send the following data (here, values are expressed

in decimal instead of binary for easier readability):

# 2 1 3 7 6 8 9 2 ...

The byte that immediately follows the # contains 2, which means that

you would have to read the two following bytes to know the length (in

bytes) of the retrieved data. The bytes indicate 1 and 3. The length will

then be 13 bytes. The actual response will begin at byte number 5, in

this case.

<non-zero

<8-bit data

<digit>

digit>

byte>

#

<8-bit data

<PROGRAM MESSAGE

0

byte>

TERMINATOR>

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Data Types

Applicable Data Types for Input—IEEE 488.2

 <SUFFIX PROGRAM DATA>

This data type is used when units and multipliers have to be sent.

/

<wsp>

/

<suf f ix mult.>

<suf f ix unit>

<digit>

-

<suf f ix unit>

<digit>

-

Examples: nm, kHz, km/s2, uW

A relative unit (dB) can be referenced to an absolute level, as shown on the

following diagram.

D/d

B/b

<suf f ix mult.>

<suf f ix unit>

Examples: db, dbm, dBW

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Data Types

Applicable Data Types for Input—IEEE 488.2

The following table illustrates the possible forms for <suffix mult.>:

Name

Value

Mnemonic

Exa

1E18

EX

Peta

1E15

PE

Tera

1E12

T

Giga

1E9

G

Mega

1E6

MA

Kilo

1E3

K

Milli

1E-3

M

Micro

1E-6

U

Nano

1E-9

N

Pico

1E-12

P

Femto

1E-15

F

Atto

1E-18

A

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Data Types

Applicable Data Types for Input—IEEE 488.2

The table below gives the possible forms for <suffix unit>:

Reference Unit

Suffix Unit

Degrees

DEG

Radians

RAD

Amperes

A

Volts

V

Hertz

HZ

Meters

M

Watts

W

DBs ref to 1mW

DBM

Decibels

DB

Degrees Celsius

CEL

Degrees Fahrenheit

FAR

Kelvins

K

Seconds

S

Hours

HR

Minutes

MIN

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Data Types

Applicable Data Types for Output —IEEE 488.2

 <NR1 NUMERIC RESPONSE DATA> (or <NR1>)

This data type will be used by a device to return positive or negative

integers.

+

<digit>

-

Examples: 4, -23, 90

 <NR2 NUMERIC RESPONSE DATA> (or <NR2>)

This data type will be used by a device to return positive or negative

real numbers (fixed-point numbers).

+

<digit>

<digit>

-

Examples: 23.45, 1.22, -4.55

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Data Types

Applicable Data Types for Output —IEEE 488.2

 <NR3 NUMERIC RESPONSE DATA> (or <NR3>)

This data type will be used by a device to return positive or negative

exponential numbers (floating-point numbers).

+

<digit>

<digit>

-

+

E

<digit>

-

Examples: 4.3E-3, -8.9456E8, 123E-5

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Data Types

Applicable Data Types for Output —IEEE 488.2

 Special Numeric Values Received on Output

In some cases, an instrument may send values indicating that an

unusual event has occurred. The following tables present the possible

values.

Value is

ASCII 4 bytes

PACKED 4 bytes

Under range

2143289345.000000

7FC00001

Over range

2143289346.000000

7FC00002

Invalid

2143289347.000000

7FC00003

Inactive

2143289348.000000

7FC00004

Value is

ASCII 8 bytes

PACKED 8 bytes

Under range

9221120237577961472

7FF8000020000000

Over range

9221120238114832384

7FF8000040000000

Invalid

9221120238651703296

7FF8000060000000

Inactive

9221120239188574208

7FF8000080000000

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