Mitsubishi Digital Electronics FX0 Manual

A SERVICE OF

next previous

FX Series Programmable Controlers Applied Instructions 5

5-7

5.1.2 CALL (FNC 01)

Points to note:

a) Man

y

CALL statements can reference a sin

g

le subroutine.

b) Each subroutine must have a unique pointer number. Subroutine pointers can be selected

from the ran

g

e P0 to P62. Subroutine pointers and the pointers used for CJ (FNC 00)

instructions are NOT allowed to coincide.

c) Subroutines are not normall

y

processed as the

y

occur after an FEND instruction. When

the

y

are called, care should be taken not to overrun the watchdo

g

timer settin

g

. For more

information on watchdo

g

timers please see pa

g

e 5-12.

d) Subroutines can be nested for 5 levels includin

g

the initial CALL instruction. As an example the

pro

g

ram shown opposite shows a 2 level nest.

When X1 is activated the pro

g

ram calls subroutine

P11. Within this subroutine is a CALL to a second

subroutine P12. When both subroutines P11 and

P12 are active simultaneousl

y

, the

y

are said to be

nested. Once subroutine P12 reaches its SRET

instruction it returns the pro

g

ram control to the

pro

g

ram step immediatel

y

followin

g

its ori

g

inal

CALL (see



). P11 then completes its operation,

and once its SRET instruction is processed the

pro

g

ram returns once a

g

ain to the step followin

g

the CALL P11 statement (

see



).

Mnemonic Function

Operands

Program steps

D

CALL

FNC 01

(

C

all sub-

routine

)

Executes the

subroutine

pro

g

ram startin

g

at the identified

pointer position

Valid pointers from the ran

g

e 0 to 62

Nest levels: 5 includin

g

the initial CALL

CALL, CALLP:

3 step

Subroutine pointer

P

PP

: 1 steps

X0

P 10CALL

FEND

SRET

P10

[ D ]

Subroutine D10

Operation:

When the CALL instruction is active it forces the

pro

g

ram to run the subroutine associated with the

called pointer (area identified as subroutine P10). A

CALL instruction must be used in con

j

unction with

FEND (FNC 06) and SRET (FNC 02) instructions. The

pro

g

ram

j

umps to the subroutine pointer (located after

an FEND instruction) and processes the contents until

an SRET instruction is encountered. This forces the

pro

g

ram flow back to the line of ladder lo

g

ic

immediatel

y

followin

g

the ori

g

inal CALL instruction.

X1

P 11CALL

FEND

SRET

P11

P 12CALL

SRET

P12

1

2