If it were me, I would likely have the SCL FB call a LAD block to handle the standard ladder logic types of things inside the SCL FB's loop.  SCL is very good for looping compared to LAD (in my opinion).

gtsolid

Hi,

i'm developing a small program for managing this kind of lubrication:

In summary:

0. Only at first start (I7.7=1 from MCP): Hydraulic unit runs for 30" (output Q42.5=1 for 30").

1. Start of the loop: Q42.5 runs until I34.3 is =1 for 5". Here Q42.5 stops until the end of the cycle (480" from the beginning of 1.)

2. Loop 1 repeating forever

Condition for which i have alarms:

1. level of oil in the tank is always above a certain level (input I34.4=1).

2. the pressure and the air flow are above a certain level (inputs I37.0=1 and I37.1=1). If I37.0=0 for 8" from the cycle start ==> error (Q42.5=0 for safety); If I37.0=0 for 3" during the cycle ==> error (Q42.5=0 for safety)

How to develop this in SCL? I would use a FC to do this. My plan was to use a TON timer to be active in the first 30" but then i don't know how to mantain a cycle

gtsolid

How to develop this in SCL?

IMHO fair approach to that class of problems. 

A little more advanced extension of above approach. 

gtsolid

Having an S7-300 I have to use old Timers.

Saying "old Timers" do you refer to S5 timers? S7-300 supports IEC timers (TON, TOF, TP) too.