EPICS Component Reference Manual
The fanout record uses several forward processing links to force multiple passive records to scan. When more than one record needs to be scanned as the result of a record being processed, the forward link of that record can specify a fanout record. The fanout record can specify up to sixteen other records to process. If more than sixteen are needed, one of the forward links in the fanout record (or its FLNK field) can point to another fanout record.
NOTE: Fanout records only propagate processing, not data. The dfanout or Data Fanout record can, on the other hand, send data to other records.
The record-specific fields are described below, grouped by functionality.
The forward link fields of the fanout record (LNK0-LNK9, LNKA-LNKF) specify records to be scanned. The records to be processed must specify Passive in their SCAN fields; otherwise the forward link will not cause them to process. Also when specifying database links for the fanout record, the user needs only to specify the record name. As no value is being sent or retrieved, a field name is only required when the link will be over Channel Access, in which case the field PROC must be named.
The SELM, SELN, and SELL fields specify the order of processing for the forward links. The select mechanism menu field (SELM) has three choices:
Index Identifier Choice String 0 fanoutSELM_All All 1 fanoutSELM_Specified Specified 2 fanoutSELM_Mask Mask
How the SELM value affects which links to process and in which order is as follows:
All Links are processed in numerical order - LNK0, LNK1, etc.
Specified The sum of the values in the SELN and OFFS fields is used as the specifier of which link to process. For instance, with OFFS=0 and SELN=1, the record targeted by LNK1 will be processed.
Mask The individual bits in SELN are shifted by SHFT bits (negative means shift left) and the result used to select which links to process as follows:
If bit 0 (LSB) is set, LNK0 is processed.
If bit 1 is set, LNK2 is processed.
If bit 2 is set, LNK3 is processed, etc.
SELN reads its value from SELL. SELL can be a constant, a database link, or a channel access link. If a constant, SELN is initialized with the constant value and can be changed via dbPuts. For database/channel access links, SELN is retrieved from SELL each time the record is processed and can also be changed via dbPuts.
The Fanout record also has the standard scanning fields common to all records. These fields are listed in Scan Fields.
Field Summary Type DCT Default Read Write CA PP SELM Select Mechanism MENU (fanoutSELM) Yes Yes Yes No SELN Link Selection USHORT No 1 Yes Yes No SELL Link Selection Loc INLINK Yes Yes Yes No OFFS Offset for Specified SHORT Yes Yes Yes No SHFT Shift for Mask mode SHORT Yes -1 Yes Yes No LNK0 Forward Link 0 FWDLINK Yes Yes Yes No ⋮ LNK9 Forward Link 9 FWDLINK Yes Yes Yes No LNKA Forward Link 10 FWDLINK Yes Yes Yes No ⋮ LNKF Forward Link 15 FWDLINK Yes Yes Yes No
These parameters are used to present meaningful data to the operator. See Fields Common to All Record Types for more on these fields.
Field Summary Type DCT Default Read Write CA PP NAME Record Name STRING [61] No Yes No No DESC Descriptor STRING [41] Yes Yes Yes No
The Fanout record has the alarm parameters common to all record types. Alarm Fields lists the fields related to alarms that are common to all record types.
The VAL field performs no specific function, but a Channel Access put to it will cause the record to process.
Field Summary Type DCT Default Read Write CA PP VAL Used to trigger LONG No Yes Yes Yes
This routine initializes SELN with the value of SELL, if SELL type is CONSTANT link, or creates a channel access link if SELL type is PV_LINK.
See next section.
Routine process implements the following algorithm:
PACT is set to TRUE.
The link selection SELN is fetched.
Depending on the selection mechanism, the link selection forward links are processed, and UDF is set to FALSE.
Check to see if monitors should be invoked:
Alarm monitors are invoked if the alarm status or severity has changed.
NSEV and NSTA are reset to 0.
Scan forward link field FLNK if used, set PACT FALSE, and return.