Real-Time Clock (Rtc) - IBM 1710 Manual

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9999, remains in the
ADC
register until the program
causes it to be transferred to core storage. An
ADC
con-
version scale is shown in Figure 7. Pertinent pro-
gramming details follow.
If a negative analog voltage is read into the
ADC,
a flag is placed over the units digit of the
ADC
register
and the Negative light on the 1711 Operator's Panel is
turned on. This flag bit is transferred to core storage
with the units digit when the transfer from the
ADC
register to core storage occurs.
If the analog signal exceeds the range of its match-
ing card, four flag bits rather than the contents of the
ADC
register are placed in core storage. The
ADC
register
and associated 1711 Operator Panel lights will contain
an 8-2 or 8-2-1 bit configuration in the high-order posi-
tion and 000-999 in the other three positions depending
on the value of the overload signal.
When the four digits from the
ADC
register are trans-
ferred to core storage, the high-order digit is flagged.
The replaced data including flag bits is lost.
Once the converted data is in core storage, the pro-
gram transforms the digital value into a meaningful
measurement of the variable (temperature, flow rate,
pressure, etc.) .
Two Program Select instructions: Select Address and
Select
ADC
Register are available for reading analog
ADC INPUT
DIGITAL
0-50 1-5 4-20 10-50
OUTPUT
Millivolt Milliamp
Milliamp Milliamp
+50 and 5 and 20 and 50 and
over
over over over
0000
+49.995
4.995 19.995 49.995
9999
+40 4
16 40
8000
+30 3
12 30
6000
+20 2 8 20
4000
+10 1 4 10 2000
0
-
- -
0000
-10 -1 -4 -10
2000
-20 -2
-8 -20
4000
-30 -3
-12 -30
6000
-40 -4
-16 -40
8000
-49.995 -4.995 19.995 -49.995
9999
-50 and -5 and 20 and 50 and
0000
under
under under under
Figure 7.
ADC
Conversion Scale
signals into the
ADC
for conversion. Select Address and
Select
ADC
Register are provided with Random Ad-
dressing of
TAS,
a special feature. The Select Address
instruction merely reads the selected signal into the
ADC
for conversion, whereas the Select
ADC
Register
transfers the contents of the
ADC
register into core stor-
age first, and then reads the newly selected analog sig-
nal for conversion.
The Multiplexer Busy indicator (29) is on during
the 50 millisecond conversion cycle. This indicator may
be interrogated to determine when conversion is com-
pleted. The computer proceeds with succeeding in-
structions during conversion unless an instruction that
uses the multiplexer is initiated (Analog Input, Analog
Output, or Contact Operate instructions) . In this case,
both the instruction and the computer are delayed
until after conversion is completed and Multiplexer
Busy is turned off.
The Multiplex Complete indicator (40) is turned
on at the end of conversion. Multiplex Complete initi-
ates an interrupt which can cause reading of the
ADC
register, selection of the next Analog Input address, etc.
It is often desirable to take successive readings of an
input variable in order to assure that no error occurred
in the measuring of the variable or in the analog-to-
digital conversion of the measurement. By taking three
separate readings, the output of all three readings may
be compared against a predetermined range. If all three
readings lie within a specified range, the first reading,
or perhaps an average of the three readings, may be
used with more certainty as the value of the input vari-
able. '!\Then this is done, a time delay of 600 ms should
be programmed between successive readings of the same
point to ensure maximum accuracy.
Real-Time Clock lRTCJ
The
RTC
designed for use in logging applications is
an electronically powered 24-hour mechanical device
which keeps time (to the nearest minute) in hours,
tenths of hours, and hundredths of hours. The contents
of the
RTC,
00.00 through 23.99, are displayed on the
1711 Operator's Panel, and may be read into core stor-
age by use of the Select Real-Time Clock instruction.
The low-order position clock wheel advances once each
minute, as follows: 0-2-3-5-7-8-0.
The
RTC
may be programmed so that the logging
time is printed along with log data. To prevent the
possibility of erroneous readings, readout of the
RTC
is blocked during the time the clock wheels advance
(approximately 320 milliseconds) .
Three levers are provided on the 1711 Operator's
Panel to set the clock. The levers travel up and down
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