Hi G H-L Ev El Messages - Tektronix 7A16P Instruction Manual

7 Α 16 Ρ IN S TR UC TI ON
Hi g h-L ev el Messages
7 Α 16 Ρ hi g h-l ev e l messages ar e device-dependent an d t he r e fo re are
n
ot s p ec ifi ed in t h e IEEE 488 sta n da rd .
H
owe v e r , t h ese hi g h-l eve l
messages do co nfo rm to
T
e k t r o nix sta nd a r ds in te nded to e nha n ce
T
e k t ro ni x
com p at i b il it y w i t h ot h e r b
u s-comp at i bl e in st r um e n ts . To acco mpli sh t hi s,
codes a nd
s
yn tax a r e des i g n e d to be un am b i g u o u s, to co rr esp o n d to t h ose
u
sed b y ot h e r T e k t ro nix devi ces, a n d to be as s imple a n d ob vi o u s as
p
oss i b l e . Th is min imi z es t h e cost a n d time
r
e quir ed to pr og r am t h e 7 Α 16 Ρ
b y m a king
i
t eas i e r f o r t h e pr ogr amm er to wri te a n d un de r sta n d t h e needed
devi ce--de p e n de n t code .
Th e 7 Α 16 Ρ
r
es p o n ds to d
e vi ce-de pe n de n t messages t h at co n ta in o n e o r
bot h o f tw o t yp es o f comma n ds : Set a nd
Q
u e ry . During α Set co mm a n d, t h e
plug- in acts as α li ste n e r an d
u
ses t h e in com ing in form at i o n to e ff ect
cer ta in o p e r at ing
m
odes o r fr o n t- pan e l sett ings . During α
Q
u e ry comman d,
t he plu g- in ini t i a lly acts as α listen e r un t il receiving an UNListen
com m a n d ; t h e n t h e plu g- in i s
m
a de α ta lke r
a
n d
r
et urn s t h e stat u s o f α
s
pec ifi ed fun ct i o n o r o p e r at ing pa r amete r . Th e s yn ta x o f α Set an d Qu e ry
comm a nd i s ex pl a in e d l ate r .
Α device-dependent
m
essage beg in s wh e n
t
h e plug-in
i
s ad dr esse d as α
talk e r or liste n e r , wi t h ΑΤΝ asse r ted . T h e n ΑΤΝ
i
s un asse r te d
a
n d t he
act u a l device-dependent code
i
s t r a n smi tted fr om tal ke r to li ste n e r . T h e
m
essage
i
s te rmin ated wh e n ΕΟΙ
i
s asse r te d . ΕΟΙ
i
s se n t con c urr e n t w i t h
t he
l
ast byte o f
t
h e
m
essage, wh et h e r i t be α data b y te, α de limi te r, o r
α fo rmat c h a r acte r .
Wh en
s
p ec i a l driv e r so f twa re
i
s be ing
u
sed, t h e
u
se r n ee d n ot
co nce rn h imse lf wit h all t h e deta il s o f i nit i at ing a n d te rmin at in g eac h
message, si n ce t hi s
i
s do n e a u tom at i call y
b
y
t
h e so f t w a r e .
M
ost o f
t
hi s
sect i o n
t
hu s dea l s w i t h message s yn tax
r
at h e r t h a n message t r a n s mi ssio n .
H
owe v e r , fo r t h ose who are
n
ot
u
s in g spec i a l driv e r software, α bri e f
d i sc u ss i o n i s in c lu ded
l
ate r as to the m
et h ods o f ini t i at ing a n d
te rmin at ing α message .