Mitsubishi Digital Electronics FX0S Manual

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FX Series Programmable Controlers Applied Instructions 5

5-62

5.6.9 PWM (FNC 58)

Operation:

A continuous pulse train is output throu

g

h device D

when this instruction is driven. The characteristics

of the pulse are defined as:

The distance, in time (msec), between two

identical parts of consecutive pulses (S

2

).

And how lon

g

, also in time (msec), a sin

g

le pulse

will be active for (S

1

).

Points to note:

a) Because this is a 16 bit instruction, the available time ran

g

es for S

1

and S

2

are 1 to 32,767.

b) A calculation of the dut

y

c

y

cle is easil

y

made b

y

dividin

g

S

1

b

y

S

2

. Hence S

1

cannot have a

value

g

reater than S

2

as this would mean the pulse is on for lon

g

er than the distance

between two pulses, i.e. a second pulse would start before the first had finished. If this is

pro

g

rammed an error will occur.

This instruction is used where the len

g

th of the pulse is the primar

y

concern.

c) The PWM instruction ma

y

onl

y

be used once in a users pro

g

ram.

d) Because of the nature of the hi

g

h speed output, transistor output units should be used with

this instruction. Rela

y

outputs will suffer from a

g

reatl

y

reduced life and will cause false

outputs to occur due to the mechanical ‘bounce’ of the contacts. To ensure a ‘clean’ output

si

g

nal when usin

g

transistor units, the load current should be 200mA or hi

g

her. It ma

y

be

found that ‘pull up’ resistors will be required.

Mnemonic Function

Operands

Program steps

S

1

S

2

D

PWM

FNC 58

(

Pulse

width

modulation)

Generates a

pulse train with

defined pulse

characteristics

K, H,

KnX, KnY, KnM,

KnS,

T, C, D, V, Z

Note:

S1

S2

Y

Note:

FX

0(S)

/FX

0N

users:

Y001 onl

y



.

FX users: an

y

Y

PPP

.

FX

2N(C)

users: Y000 or

Y001 onl

y



PWM:

7 steps

g

)FX

(2C)

and FX

2N(C)

units can use the HSZ (FNC 55) instruction with the PLSY instruction

when source device S

1

is set to D8132. Please see pa

g

e 5-59 for more details.

h) FX units with CPU version 3.07 or

g

reater and FX

2C

units can monitor the number of pulses

which have been output as a double word usin

g

devices D8136 and D8137.

FX

2N(C)

units can also monitor the number of pulses output to Y0 usin

g

devices D8140 and

D8141 and the number of output pulses output to Y1 usin

g

devices D8142 and D8143. The

total number of pulses output can be monitored usin

g

D8136 and D8137.

X10

K50D10 Y 0PWM

[ S1 ]

[ S2 ] [ D ]

D

S1

S2