HP 59313A Operating And Service Manual page 119

T he co mm ands se rve severa l d
if ferent pu rposes :
Table Α 1. Comman
d and
Add
r
ess Codes
A
pp e ndix Ι - Th e HP Interface Bu s
M
ode l 59313 Α
Th e co ntrol ler has two ways of send in g in terface m
essages. Multiline messages, whi c h cannot exi st co ncu rren tl y
with ot he r mult ili ne messages, are sent over t he eigh t
d
ata l ines and the three transfer-bus lines. Unil ine
m
essages
are transferred ov er tile
f
ive individual li n es of t he m
anagement bu s.
(1) A
ddr
esses,
o
r talk and liste n commands, select the inst ruments t h at will transm it and accept data .
They are all multil in e messages .
(?)
U
ni
ve
r
sa
l
cο
m
ηταιτds ca use every instrument equi pp ed to do so to
p
er f orm α
s
pecific i nte rf ace
operatio n. Th ey i n cl ud e mu ltil ine messages and three
u
niline commands, i n te r face clea r (IFC), r
emote enable
(REN), a nd attention (ATN).
(3) A
d
dresse d
co
m
man d
s are sim ilar to universal co mmands, except th at th ey affect only those
d
evices t hat are add ressed a n d are all mu ltiline comm an ds. An instrument responds to an addresse d co mma nd ,
however, only after an a d dress
h
as alr eady told it to be α talker or listener .
(4) Secοιτdαrv com
m
ands
a
re mu ltili ne messages that are always
u
sed i n series with an add r ess,
un iversal command, or ad dr essed co mm and (also r
eferred to as primary comm ands) to form α longer ve rsi on of
each.
T
h us they exten d the code space when necessary.
To ad d ress an in st ru ment, the co ntrolle r u ses seven of the eight data-bus lines. This allows inst ruments using the
ASCII 7-bit code to act as controllers .
A
s shown in Table Al , five data bits are avail able for addresses, so α total
o f 31 a dd resses is available in one b
yte . If all secondary comm ands are
u
sed to exte nd this in to α two-byte
addressi ng ca p ab il ity, 961 addresses beco me available (31 addresses i n the seco nd byte
f
o r each
o
f the 31 in the
f
i rst byte).
Co de
F
o rm
M
eaning
Χ 0 0 Α5 Α4 Α3 ΑΖ Α 1
Universal Co mm a nd s
Χ 0 1 Α5 Α4 Α3 ΑΖ Α 1
L
iste n Addresses
exce pt
Χ
0 1 1 1 1 1 1 Un listen Co m ma nd
Χ 1
0
Α5
Α4 Α 3 ΑΖ Α 1 Tal k Addresses
exce pt
Χ 1
0
1 1
1 1 1 Un talk Co mm an d
Χ 1 1 Α 5 Α4 Α3 ΑΖ Α 1 Seco nd ary Command s
exce pt
Χ 1 1 1 1 1 1 1 Ignored
(Code
u
sed wh en attention ( ΑΤΝ ) is true οπω )