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3.14
10745A HP-IB Interface
The
10745A
HP-IB
lnterface i s
an
appropriate
laser
transducer
input/output
(I/O)
module
for
any
system
controller
that
is
compatible
with
the
HP
Interface
Bus
(IEEE
Standard
488-1975).
Such
controllers
include
Hewlett-Packard
Models
9815A, 9820A,
9821A,
9825A,
9830A,
9835A,
and
9845A
Calculators,
HP
2100
Series
Computers
with
the
593108
1/O
card,
or
any
HP-IB
compatible
user-built
controller.
Figure
3-77
is
a
block
diagram
of
the
HP-IB
card.
Error
Bits
4
4,
I
I
I
raRl6WI
Binary to
Character
Sorlal BCD
Converter
and W m a l
Polnt
Code
clmn
I
.
SRQ
I
I
Character
*&Bit
&
-
Parallel
Data
Data
In
I
I
1
14
I
4-Bit
b z
71
Decimal
Decimal
Point
Code
Point
'ASCII
Qualifier
Coda
Data
Load
Iemory, Talke
State Machine
Error Butfar
and S e ~ l c a
Ieqmt Clrcul
Valid
Card
Address
operation
C ,
Complete
I
and
Backplane Handshake Clmults
P
HP-IB
Transceiver-
i
Commcmc
and A dd-
Handshake
Cimlts
INW
Valid
&
Instruction
coupler
Backplane
I
~
e
s
I
IFC
I
I
1
ATN
I
I
--)
DAV
I
--)
NRFD
I
HP-IB
- -
Figure
3-77.
70745A
~ ~ - 1 ~ l ; t e r f a c e
~ l o c k
Diagram
The HP-IB card can operate as either a talker or a listener on the HP-IB. As a talker, it has two
modes of operation. First, when addressed to talk, it outputs a string of nine ASCII (American
Standard Code for Information Interchange) numeric digits followed by ASCII carriage re-
turn (CR) and line feed (LF) codes. A decimal point, also in ASCII, can occur anywhere in the
string of digits.
The HP-IB card's second mode of operation a s a talker is related to the service request capa-
bility and the serial poll mode. When an error in the laser transducer system is noted by any
card, the card involved stores the occurrence in a buffer. When that card is instructed to output
its data, it also outputs the contents of its error buffer. This error information is loaded into an
error register on the HP-IB card and can only be cleared with a reset command. The presence
of the error condition causes the HP-IB line called SRQ to be set true. The controller should be
programmed so that, when it recognizes
this
condition,
it
executes a serial poll, that is, it un-
talks and unlistens everything on the bus, then addresses itself to listen and sends the universal
command SPE (Serial Poll Enable). Then it begins polling devices on the HP-IB capable of
responding to SPE by sequentially addressing them to talk. Responding to serial poll, the
HP-IB card outputs an eight-bit status byte. The controller takes the decimal value of the
status byte and examines it to see if bit 6, the service request bit, is set or not. If it is, bits 0
through 3 are examined to see what combination of errors has occurred. The controller may
then send a reset command to clear the error register of the HP-IB card.
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Table of Contents
Troubleshooting
