Agilent Technologies HP 82335, Install Manual, Page: 36 / 54

HP-IB Fundamentals
HP-IB Description
HP-IB Description
The Hewlett-Packard Interface Bus (HP-IB) is HP's implementation of the
IEEE-488 communication interface. It is used by a variety of instruments,
disk drives, and peripherals manufactured by Hewlett-Packard Company
and other companies.
HP-m is a 16-line bus that connects up to 15 devices
in parallel on a communication link.
Figul"� A·I shuws lhe HP-IS t:unneclor.
SIGNAL GND
ht.t.d
Pair
lit
t� 11
�"'�'"
�
rllt.ted Pal� .t lh
"
Tlli�t"d
Pair "I
th
,
,,�
hl,t.d
Pair
.t th
,
rlll.t"d
P.l�
.ith
,
Tllt,ted Pd,
.i th
,
'"
0106
0101
0106
DIOS
THE i"f>-IB LOGIC LEVELS
ARE TTL COMPATIBLE:
TRUE STATE
<- 0.5
V
FALSE STATE >= 2.0 V
"
23
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Figure A-1 . HP-IB Connector
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SHIELD GND
U
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,
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,
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,
• 0104
,
0103
,
0102
,
0101
Of the 16 signal lines, 8 are data lines. J are for handshake purposes, and the
remaining 5 are control lines. Information is transferred across the eight data
lines
in a bit-parallel, byte-serial fashion. Briefly, the eight control and
handshake lines are used as follows:
ATN
EO!
A
Attention is used primarily to differentiate between Command
mode and Data mode. When A
TN
is true, infonnation on the
data lines is interpreted as a bus command; when ATN is false,
the information is treated as a data byte.
End Or Identify has two uses. EOI is assened on the last byte
of a data transfer-this signals all listening devices that no
more data should be expected on the transfer. EOI is used in
combination with ATN to perform a parallel poll.
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