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SECTION 4
GPIB Interface
4.3.4
Receive and Transmit
Codes
Receive Codes in Listener Mode
IS0 7-bit codes (JIS/ASCII)
are used. The MSB (parity
bit) of &bit data is ignored. Uppercase letters and lower-
case letters are treated the same.
<Effective letters>
!"#$%&'()*+,-./
0123456789:<=>?@
ABCDEFGHIJKLMNOPQRSTUVWXYZ
I*1 A-r
abcdefghijklmnopqrstuvwxyz
II I-
+ is only for the JIS code. For the ASCII code, a backslash is
assigned.
The characters other than the above (control code includ-
ing space, semicolon, and tab) are ignored and do not en-
ter the receive buffer. <CR> (carriage return) and <LF>
(line feed) are effective only for the delimiters indicating
the end of the program code.
Transmit Codes in Talker Mode
IS0 7-bit codes (JIS/ASCII) are used without parity code
(MSB of 8-bit data = 0). Alphabet is transmitted in upper-
case letters.
4.3.5
Delimiters
In Listener Mode (when the instrument
receives)
Any <CR>, <LF> or END message (EOI line in data trans-
fer mode = LOW: True), or all of their combinations
can
be accepted.
In Talker Mode (when the instrument
transmits)
<CR> or <CR> <LF> -The
END message is output with
the last letter (of a delimiter) of the transmit data.
4.3.6
Program Codes
The instruction
used to control the instrument
over the
GPIB or to read the setting or measured data is called a
program code. The program code is classified as follows.
0 Setting message: Performs setting or operation
com-
mand.
l
Inquiry message: Reads setting or measured data.
Execution
A program
code is stored in the receive buffer, inter-
preted when its delimiter is received, and then executed.
When the execution
terminates,
the receive
buffer
is
cleared and ready for the next receive.
Receive Buffer
Capacity of buffer: 256 letters. A space, semicolon, <CR>
and <LF> do not enter the receive buffer.
When the instrument receives a long program code in ex-
cess of the capacity of receive buffer and the buffer over-
flow, an error results. In this case, all the codes are ig-
nored, and the receive buffer is cleared.
Basic Syntax
The
basic
syntax
of the
program
code
is shown
Figure 4-4.
SP : Space code
; : Semicolon code
Header
: Programs a major category such as functions,
operation objects.
Parameter : Values to be set expressing selection
Delimiter
: Indicates the end of a program code.
Figure 4-4.
Basic Syntax Program Code
Program codes can be sent successively
within the capac-
ity of receive buffer. When sending program codes suc-
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4-7
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