Philips PM2519 - Page 35

2-19
2.4.4. Measuring sequence
After power on, the PM 2519 carries out some routines to measure and evaluate the input signal applied.
The software applications are briefly indicated by the following sequence.
After power on the microcomputer
fills RAM locations in the P with the
status of the instrument e.g.
Auto-ranging
MONITOR
In this phase the microcomputer looks
whether an interface is connected and
if so, checks if it has to do something
external.
YES
EXTERNAL ?
FUNCTION
TEST?
DATA HOLD
TEST?
READY TEST ?
DECREMENT
COUNTER
COUNTER
=0?
This routine reads the function switch
(port 0) and updates the function
register. It also checks if the function
switch has been changed.
This routine checks if a DATA HOLD
probe is connected and if so, it “reads”
the probe (e.g. freeze the display).
The ready test reads the ready signal
coming from the ADC interface.
If not present, it decrements the counter
until a ready occurs. This sequence is
executed until the counter becomes
zero. At that time the set-up routine
is called to set-up the ADC interface
once again, otherwise it would stay in
that sequence,
MEASURE COMPUTE
ST4412
840629
QUTPUT |
Fig. 2.18. Flowchart measuring sequence