january 2009epics seminar in indore1 introduction to state notation language (snl) tatsuro nakamura...

January 2009 EPICS Seminar in Indore 1

Introduction toState Notation Language (SNL)

Tatsuro NAKAMURA @ KEK

January 2009


Outline

• 1. Introduction

• 2. Basic Feature

• 3. Additional Feature


1. IntroductionSNL and Sequencer

• SNL (State Notation Language)– A programming language like C– Based on the State Transition Diagram– SNC : State Notation Compiler

• Sequencer– Programs produced by the SNL are executed

within the framework of the run-time sequencer.


State Transition Diagram

State A

State B

State C


Where Sequencer runs ?

• Typical usage --- runs in IOC– Sequencer is a software component of IOC.

process database

Sequencer

CA

IOC

OPI

process database

CA

network


• Another usage --- runs in OPI– Sequencer (Ver. 2.0 or later) can run as a

stand-alone program in workstation.

process database

Sequencer

CA

IOC

OPI

process database

CA

Sequencer

network


Documents

• EPICS Sequencer Page– http://

www.slac.stanford.edu/comp/unix/package/epics/sequencer/

• Manual is available.

• Tutorial Slides– http://www.aps.anl.gov/epics/docs/USPAS2007.php

http://www.slac.stanford.edu/comp/unix/package/epics/sequencer/




http://www.aps.anl.gov/epics/docs/USPAS2007.php


2. Basic Feature

• State Transition Diagram

Start

Light is off

Light is on

v > 60

Turn light on

v < 50

Turn light off

event

action

statestate transition


First Step of SNL Code

• Skeleton of the SNL codestate light_off

{

when (v > 60.0) {

/* turn light on */

} state light_on

}

state light_on

{

when (v < 50.0) {

/* turn light off */

} state light_off

}

Start

Light is off

Light is on

v > 60

Turn light on

v < 50

Turn light off


Variables assigned to a Channel

short light;

assign light to "sample:IndicatorLight";

/* turn light on */

light = TRUE;

pvPut(light);

/* turn light off */

light = FALSE;

pvPut(light);


Monitor a Channel

float v;

assign v to "sample:Vout";

monitor v;

when (v > 60.0) { …


A Complete State Programprogram seqtestfloat v;assign v to "sample:Vout";monitor v;short light;assign light to "sample:IndicatorLight";ss volt_check{

state light_off{

when (v > 60.0){

/* turn light on */light = TRUE;pvPut(light);

} state light_on}

state light_on{

when (v < 50.0){

/* turn light off */light = FALSE;pvPut(light);

} state light_off}

}


Structure of a State Programprogram seqtestfloat v;assign v to "sample:Vout";monitor v;short light;assign light to "sample:IndicatorLight";ss volt_check{

state light_off{

when (v > 60.0){


} state light_on}

state light_on{

when (v < 50.0){


} state light_off}

}

Program

Definition

State Set


Structure of a State Set

Event Action(State Transition)

State

State Set

program seqtestfloat v;assign v to "sample:Vout";monitor v;short light;assign light to "sample:IndicatorLight";ss volt_check{

state light_off{

when (v > 60.0){


} state light_on}

state light_on{

when (v < 50.0){


} state light_off}

}


program seqtest2 … declaration …ss state_set_1{

state A{ …}state B{ …}

}ss state_set_2{

state C{ …}state D{ …}

}

Multiple State Sets

State C

State D

State_set_2

State A

State B

State_set_1

Each State Set runs concurrently.


Declaration (1)

• Variable

int variable_name;

short variable_name;

long variable_name;

char variable_name;

float variable_name;

double variable_name;

string variable_name; … fixed size char array


Declaration (2)

• Assign

• Monitor

assign variable_name to "channel_name";

monitor variable_name;


Declaration (3)

• Array of Variables

– int, short, long, char, float, double variable can be array. (array of string is not available.)

int variable_name[array_length];

int variable_name[array_length][array_length];

int Vin[4];

assign Vin to {"chan1", "chan2", "chan3"};

monitor Vin;


Events

• Typical expression:– Change in value of a variable

– Time out

• The delay function returns a TRUE after a specified time interval from when the state was entered.

• It should be used only within when expression.• Its argument must contain a decimal point.

when (v > 60.0)

when ( expression )

when (delay(10.0))


Actions (1)

• Most C statements are supported.

expression;

if (…) … else …

while (…) …

for (…, …, …) …

break;


Actions (2)

• C code may be escaped in the program.

%% escape one line of C code

%{

escape any number of lines of C code

}%


Actions (3)

• Built-in functionspvPut(variable_name)

pvGet(variable_name)

…– You can see many built-in functions in the ma

nual. – In principle, the built-in functions cannot be dir

ectly used in escaped C code.


Build an SNL program

• “make” automates the following steps.

CPP

test.st test.ctest.i test.o

SNC CC

test.stt test.c test.o

SNC CC


3. Additional Feature

• Variable Names using Macros

assign vin to "{unit}:ai1";

assign vout to "{unit}:ao1";

– Macro value is given at run-time.


• Dynamic Assignment

float Xmotor;

assign Xmotor to "";

…

pvAssign(Xmotor, "Motor_1_4");


• Status, Severity, Time stamp

pvStatus(Xmotor)

pvSeverity(Xmotor)

pvTimeStamp(Xmotor)


• Event Flag– Synchronizing State Sets using Event Flag

evflag flag1;… efSet(flag1); efClear(flag1);… when (efTestAndClear(flag1)) { … }


• Event Flag associated to a Channel– Event Flag is set whenever a monitor is delivered.

double loLimit;

assign loLimit to "demo:loLimit";

monitor loLimit;

evflag loFlag;

sync loLimit loFlag;

…

when (efTestAndClear(loFflag))

{ … }


• Connection Management

when (pvConnectedCount()!=pvChannelCount())

{ … }

when (pvConnected(Xmotor))

{ … }

– SNC compiler option•-c : don’t wait for channel connection•+c : wait for channel connection (default)


• Asynchronous pvGet(), pvPut()

pvGet(vin, ASYNC)pvPut(vout, ASYNC)…pvGetComplete(vin)pvPutComplete(vout)

– SNC compiler option•-a : synchronous pvGet() (default)•+a : asynchronous pvGet()


• Reentrant Object Code

– SNC compiler option•-r : Run-time code is not reentrant, thus saving

start-up time and memory (default)•+r : Run-time code is reentrant. More than one

instance of the state program can run on an IOC.


• More features

– Look at the tutorial slides at APS.

– Read the manual.