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In the "command" mode, the 10746A treats all computer outputs a s commands. If a command
from the computer instructs the 10746A to go to the "data" mode, the 10746A treats the next
two 16-bit words (or four &bit words, if jumper selected) a s data. The most-significant word
must be transferred first.
Two instructions cause "data" mode operation. These instructions initiate computer data out-
puts and computer data inputs. At the end of a data transfer, the 10746A returns to the "com-
mand" mode.
If the 10746A is in "command" mode, all instructions sent by the computer are passed on to
the 10740A Coupler backplane. The instructions are also examined simultaneously by the
10746A to determine if they require specific responses by the 10746A.
Use
Tables
4-2
through
4-11
to
organize
the
operating
sequence
necessary
to
provide
desired
system
operation.
For
example,
Table
4-3
shows
that
an
0 P
instruction
generates
a
backplane
reset
signal
and
clears
the
error-bit
buffer
on
the
10746A
Binary
Interface.
To
generate
this
instruction
from
the
computer,
output
the
binary
equivalent
of
the
decimal
number
shown
for
dP
in
Table
4-3
(decimal
255
or
binary
11111111)
for
a'
negative-true
interface
card.
The
10746A
Binary
lnterface
uses
positive-true
logic.
The
decimal
instructions
in
Tables
4-2
through 411
show
the
decimal
negative-true
logic
value
in
black
and
the
positive-true
logic
in
red.
Table
4-2.
70745A
UP-IB
lnterface
Instructions
BACKPLANE
CARD
ADDRESS
IS
0
ADDRESSED
INSTRUCTIONS
Response
l
nstruction
I
Decimal
BO
Generate
system
reset,
clear
error-bit
buffers
and
initialize
1 5
all
state
machines
240
*fi
Clear
error
bit
buffer
-
I
l o
1
Generate
simultaneous
sample
command
2 0
Handshake
and
do
nothing
13
242
Load
HP-IB
data
buffer
and
handshake
in
response
to
BP-DAV
-
Convert
data
stored
in
data
buffer
from
binary
to
BCD
and
store
12
in
RAM.
Output
according
to
HP-IB
rules
1
243
I
"
I
Do
nothing.
This
instruction
causes
HP-IB
to
drive
instruction
lines
passive
-
high
NONADDRESSED
INSTRUCTIONS
System
Reset
S a m e
as
BO
instruction
Sample
Do
nothing
*s
means
CMD
2
and
any
card
address
except
0
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