HP 3468A - Page 77

Example 1. Data Ready SRO
Data Ready is a feature of the 3468A that allows it to interrupt the controller
after each completed measurement (data ready). This means that the controller
doesn’t waste valuable computing time waiting for measurement data but pro-
ceeds with its work until interrupted. To enable the data ready feature on the
3468A, bit O on the SRO mask must be set. Remember that bit O will be true in
the status register anytime data is ready but for the SRO to occur the mask must
be set. The bit pattern for the mask would look like:
bit#: 5 4 3 2 1 +40
value: O O O O O 1
Ne”
Neen”
0 ‘t 01 is the octal representation
{see also Figure 4-4)
Consequently, we would use the command: OUTPUT 901;”M0O1" to set the mask
for Data Ready. Therefore, whenever the 3468A has data ready it will interrupt
the controller via the SRQ. The controller will only be interrupted if bit O is true,
|
meaning
that
data
is
ready.
Bits
1
through
5
will
not
interrupt
the
controller
if
they go true because the mask was not set for those bits. When data becomes
ready, the SRO annunciator turns on in the display, and remains on, until the con-
troller responds by doing a serial poll, executing the CLEAR command, or entering
a measurement form the 3468A.
How would this look in a simple -hp- Model 85 program?
Line Description
| 40 Puts the interface into the remote mode.
|
50
Outputs
the
SRO
mask.
ue
,
ora
See
eaten
60
Instructs
the
computer
where
to
go
(line
3h | 346SA AT ADDRESS 9a jeool when an interrupt (SRO) occurs on
& RE
oo Bae NE Sana cher 70 ENABLE INTRQ;8 actually enables the -hp-
66 OM
INTR
9
G
Model
85
to
respond
to
the
SRO.
SROQ
is
octal code “8” in the -hp- Model 85 con-
YB ENABLE INT 3 +
88
!
The
bode
of
the
Program
30
trol
register.
asa
80-990
These
lines
contain
the
main
body
of
the
ioe
program
1416
1000
This is the start of the interrupt
iw2@ OISP R
subroutine.
SPOLL returns the 3468A
1938 RETURN
status byte to variable “P”. It also resets
bit 6, if it was set, of the status register.
1010-1030 Line 1010 reads the data and resets bit 0
of the status register. Line 1020 displays
the data. Line 1030 returns program con-
trol to where the program was interrupted.
73