Motorola Axiom CMD11E1 Betriebsanweisung PDF herunterladen (Seite 97)

9.7. A SIMPLE DIGITAL VOLTMETER 97

scanning mode, there is no need to issue any new commands. Measure the

input voltage, V and compute

255V

. Also note down the values in locations

$1031-$1034. Fill in the following table for diﬀerent input voltages and

verify your results.

Measured

255

´k j

255

´k

Memory dump

Voltage (V) In Decimal In Hex $1031 $1032 $103 $1034

9.7 A simple digital voltmeter

We can write a simple voltmeter program to measure voltages in the zero to 5

volts range. Since the output is intended for human eyes, we want the output

to be in decimal. We will use one decimal accuracy so that the numbers will be

between 0 and 50 (decivolts) and we will put a decimal point between the two

digits. To convert the digital values to decivolts, we need to multiply by 50 and

then divide by 255. The steps are as follows:

1. Turn the A/D on and wait the required 100 microseconds

LDAA #%10000000

STAA OPTION

LDAA #40

DECA

BNE LT

2. Initiate conversion with SCAN=1, MULT=0, PIN=3

LDAA #%00100011 *SCAN=1, MULT=0, PIN = 011 (PE3)

STAA ADCTL

3. Make sure that the conversion is complete

WCCF

LDAA ADCTL

ANDA #%10000000

BEQ WCCF

1 2 ... 92 93 94 95 96 97 98 99 100 101

Keine Kommentare

Motorola Axiom CMD11E1 Betriebsanweisung Seite 97