Table of Contents Previous Chapter Chapter 6: bi - Binary Input

Chapter 6: bi - Binary Input

1. Introduction

The normal use for this record type is to obtain a binary value, i.e. a value that is 0 or 1. Most device support modules obtain values from hardware and place the value in RVAL. For these devices record processing sets VAL = (0,1) if RVAL is (0, not 0). Devices may optionally read a value directly into VAL. Soft device modules are provided to obtain input via database or channel access links or via dbPutField or dbPutLink requests. Two soft device support modules are provided. One allows VAL to be an arbitrary unsigned short integer. The other reads the value into RVAL just like normal hardware modules.

2. Field Summary

Field  Type       DCT  Initial  Access  Modify  Rec Proc   PP   
VAL    ENUM       No   0        Yes     Yes     Yes        Yes  
INP    INLINK     Yes  0        No      No      N/A        No   
ZSV    GBLCHOICE  Yes  0        Yes     Yes     No         Yes  
OSV    GBLCHOICE  Yes  0        Yes     Yes     No         Yes  
COSV   GBLCHOICE  Yes  0        Yes     Yes     No         Yes  
ZNAM   STRING     Yes  Null     Yes     Yes     No         Yes  
ONAM   STRING     Yes  Null     Yes     Yes     No         Yes  
RVAL   ULONG      No   0        Yes     Yes     Yes        Yes  
ORAW   ULONG      No   0        Yes     No      No         No   
MASK   ULONG      No   compute  Yes     No      No         No   
LALM   USHORT     No   0        Yes     No      No         No   
MLST   USHORT     No   0        Yes     No      No         No   
SIOL   INLINK     Yes  0        No      No      N/A        No   
SVAL   USHORT     No   0        Yes     Yes     No         No   
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 Field         This is the value resulting from record processing unless     
                          soft device support with a constant INP is chosen. If the     
                          later is chosen, VAL, which is an unsigned short, is given    
                          values via dbPuts.                                            
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.                               
ZSV   Zero Severity       Alarm Severity for state zero.                                
OSV   One Severity        Alarm Severity for state one.                                 
COSV  Change of State     Alarm Severity for change of state.                           
ZNAM  Zero Name           ASCII string defining state zero.                             
ONAM  One Name            ASCII string defining state one.                              
RVAL  Raw Value           RVAL is the value obtained by the device support routine.     
ORAW  Old Raw Value       ORAW is used to decide if monitors should be triggered for    
                          RVAL at the same time monitors are triggered for changes      
                          in VAL.                                                       
MASK  Hardware mask                                                                     
LALM  Last Alarmed Value  Value when last change of state alarm was issued.             
MLST  Last Monitored      Value when last monitor for value changes was triggered.      
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


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 device 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.


Retrieves ASCII string corresponding to VAL.


Retrieves ASCII strings for ZNAM and ONAM.


Checks if string matches ZNAM or ONAM, and if it does, sets 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. Convert
        PACT = TRUE
        TIME = tslocaltime
        if status is 0, then set VAL=(0,1) if RVAL is (0, not 0) and UDF = False
        if status is 2, set status = 0
  5. Check alarms: This routine checks to see if the new VAL causes the alarm status and severity to change. If so, NSEV and NSTA and LALM are set. Note that if VAL is greater than 1, no checking is performed.
  6. Check to see if monitors should be invoked:
  7. Scan forward link if necessary, set PACT FALSE, and return.

6. Device Support

Fields Of Interest To Device Support

Each input record must have an associated set of device support routines. The primary responsibility of the device support routines is to obtain a new raw input value whenever read_bi 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                                                                        
NSEV  New Alarm Severity                                                                   
NSTA  New Alarm Status                                                                     
VAL   Value Field         This field is set by a device support routines only if it        
                          doesn't want record support to set it.                           
INP   Input Link          This field is used by the device support routines to locate      
                          its input.                                                       
RVAL  Raw Value           It is the responsibility of the device support routine to give   
                          this field a value.                                              
MASK  Hardware mask.      The device support routine must give this field a value if it    
                          needs to use it.                                                 

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

Two soft device support modules Soft Channel and Raw Soft Channel are provided for input records not related to actual hardware devices. The INP link type must be either CONSTANT, DB_LINK, or CA_LINK.

Soft Channel

read_bi always returns a value of 2, which means that no conversion is performed.

If the INP link type is constant, then the constant value is stored into VAL by init_record, and UDF is set to FALSE. VAL can be changed via dbPut requests. If the INP link type is PV_LINK, then dbCaAddInlink is called by init_record.

read_bi 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_bi sets UDF to FALSE. The status of recGblGetLinkValue is returned.

Raw Soft Channel

This module is like the previous except that values are read into RVAL. read_bi returns a value of 0. Thus the record processing routine will force VAL to be 0 or 1.

Table of Contents Next Chapter