Table of Contents Previous Chapter Chapter 34: stringin - String Input

Chapter 34: stringin - String Input

1. Introduction

The stringin record is used to input an arbitrary ASCII string.

2. Field Summary

Field  Type       DCT  Initial  Access  Modify  Rec Proc   PP   
VAL    STRING     Yes  Null     Yes     Yes     Yes        Yes  
OVAL   STRING     No   Null     Yes     No                 No   
INP    INLINK     Yes  0        No      No      N/A        No   
SIOL   INLINK     Yes  0        No      No      N/A        No   
SVAL   STRING     No   Null     Yes     Yes     No         Yes  
SIML   INLINK     Yes  0        No      No      N/A        No   
SIMM   GBLCHOICE  No   0        Yes     Yes     No         No   
SIMS   GBLCHOICE  Yes  0        Yes     Yes     No         No   

3. Field Descriptions

Name  Summary            Description                                                   
VAL   Value              An arbitrary ASCII string of 40 characters. It is either      
                         obtained from INP or else given a value via dbPuts.           
OVAL  Output Value       Old ASCII string. Used to decide when to invoke               
                         monitors.  If VAL differs from OVAL, monitors will be         
INP   Input Link         This field is used by the device support routines to obtain   
                         input.  For soft records, it can be a constant, a database    
                         link, or a channel access link.                               
SIMM  Simulation Mode    Simulation mode process variables.  Refer to Chapter 3,       
                         Section "Simulation Mode" on page 11 for more                 
SIML  Simulation Mode                                                                  
SVAL  Simulation Value                                                                 
SIOL  Simulation Value                                                                 
SIMS  Simulation Mode                                                                  
      Alarm Severity                                                                   

4. Record Support Routines

Three record support routines are provided: init_record, process, and get_value.


This routine initializes SIMM with the value of SIML if SIML type is CONSTANT link or creates a channel access link if SIML type is PV_LINK. SVAL is likewise initialized if SIOL is CONSTANT or PV_LINK.

This routine next checks to see that device support is available and a record support read routine is defined. If either does not exist, an error message is issued and processing is terminated.

If device support includes init_record, it is called.


See next section.


Fills in the values of struct valueDes so that they refer to VAL.

5. Record Processing

Routine process implements the following algorithm:

  1. Check to see that the appropriate device support module exists. If it doesn't, an error message is issued and processing is terminated with the PACT field still set to TRUE. This ensures that processes will no longer be called for this record. Thus error storms will not occur.
  2. readValue is called. See Chapter 3, Section "Simulation Mode" on page 11 for details.
  3. If PACT has been changed to TRUE, the device support read routine has started but has not completed reading a new input value. In this case, the processing routine merely returns, leaving PACT TRUE.
  4. TIME is set to tslocaltime
  5. Check to see if monitors should be invoked.
  6. Scan forward link if necessary, set PACT FALSE, and return.

6. Device Support

Fields Of Interest To Device Support

Each stringin input record must have an associated set of device support routines. The primary responsibility of the device support routines is to obtain a new ASCII string value whenever read_stringin is called. The device support routines are primarily interested in the following fields:

Name  Summary            Description                                                   
PACT  Processing Active  See Chapter 2, Section "Database Common: Field                
                         Descriptions" on page 4 for descriptions.                     
DPVT  Device Private                                                                   
UDF   VAL Undefined                                                                    
VAL   Value              This field is set by the device support routines.             
INP   Input Link.        This field is used by the device support routines to locate   
                         its input.                                                    

Device Support Routines

Device support consists of the following routines:


  report(FILE fp, paddr)
Not currently used.


This routine is called once during IOC initialization.


This routine is optional. If provided, it is called by the record support init_record routine.


  get_ioint_info(int cmd,struct dbCommon *precord,IOSCANPVT *ppvt)
This routine is called by the ioEventScan system each time the record is added or deleted from an I/O event scan list. cmd has the value (0,1) if the record is being (added to, deleted from) an I/O event list. It must be provided for any device type that can use the ioEvent scanner.


This routine must provide a new input value. It returns the following values:

7. Device Support For Soft Records

This module places a value directly in VAL.

If the INP link type is constant, the double constant, if non-zero, is converted to a string and stored into VAL by init_record, and UDF is set to FALSE. If the INP link type is PV_LINK, then dbCaAddInlink is called by init_record.

read_stringin calls recGblGetLinkValue to read the current value of VAL. See Chapter 3, Section "Soft Input" on page 10 for details.

If the return status of recGblGetLinkValue is zero, then read_stringin sets UDF to FALSE. The status of recGblGetLinkValue is returned.

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