Mitsubishi Digital Electronics FX Manual

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FX Series Programmable Controlers Applied Instructions 5

5-53

5.6.1 REF (FNC 50)

Operation:

Standard PLC operation processes output and input

status between the END instruction of one pro

g

ram

scan and step 0 of the followin

g

pro

g

ram scan. If an

immediate update of the I/O device status is required

the REF instruction is used. The REF instruction can onl

y

be used to update or refresh blocks of

8 (n) consecutive devices. The head address of the refreshed devices should alwa

y

s have its

last di

g

it as a 0 (zero), i.e. in units of 10.

5.6.2 REFF (FNC 51)

Operation:

PLC’s are provided with input filters to overcome

problems

g

enerated b

y

mechanical switch

g

ear.

However, as this involves ensurin

g

a stead

y

input

si

g

nal is received for a fixed time duration, the use of

input filters slows down the PLC response times. For hi

g

h speed applications, especiall

y

where

solid state switchin

g

provides the input si

g

nal, input filter times ma

y

be reduced. The default

settin

g

for the input filters is approximatel

y

10 msec. Usin

g

this instruction input filter times of 0

to 60 msec ma

y

be selected. The settin

g

‘0’ (zero) is actuall

y

50

µ

sec. This is the minimum

available settin

g

. It is automaticall

y

selected when direct input, interrupts or hi

g

h speed countin

g

functions are used. The REFF instruction needs to be driven for each pro

g

ram scan if it is to be

effective, otherwise, the standard 10 msec filter time is used.

Mnemonic Function

Operands

Program steps

Dn

REF

FNC 50

(

Refresh

)



å

Forces an

immediate update

of inputs or

outputs as

specified

X, Y



Note:

D should alwa

y

s be a

multiple of 10, i.e. 00,

10, 20, 30 etc.

K, H



Note:

n should alwa

y

s be a

multiple of 8, i.e. 8, 16,

24, 32 etc.

REF, REFP:

5 steps

Mnemonic Function

Operands

Program steps

n

REFF

FNC 51

(Refresh

and filter

ad

j

ust)

Inputs are

refreshed, and

their input filters

are reset to the

newl

y

desi

g

nated

value

K, H,



Note: n= 0 to 60 msec (0 = 50

µ

s)

X000 to X007 (X000 to X017 for FX

2N

) are

automaticall

y

desi

g

nated when usin

g

this

instruction

REFF,

REFFP:

3 steps

X0

X 10

[ D ]

K 8REF

[ n ]

Note:

A short dela

y

will occur before the I/O device is ph

y

sicall

y

updated, in the case of inputs

a time equivalent to the filter settin

g

, while outputs will dela

y

for their set ener

g

ized time.

X10

K 1

REFF

[ n ]