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Spooling State Model

1. Overview

The Spooling capability allows the equipment to store messages that cannot be delivered to the host due to communication failure. When communication is restored, spooled messages are transmitted to the host in order.

2. Spooling State Diagram

stateDiagram-v2 [*] --> SPOOL_INACTIVE SPOOL_INACTIVE --> SPOOL_ACTIVE: Communication Lost & Spooling Enabled SPOOL_ACTIVE --> SPOOL_TRANSMITTING: Communication Restored SPOOL_TRANSMITTING --> SPOOL_INACTIVE: All Messages Transmitted SPOOL_TRANSMITTING --> SPOOL_ACTIVE: Communication Lost Again SPOOL_ACTIVE --> SPOOL_INACTIVE: Spool Purged / Disabled SPOOL_ACTIVE --> SPOOL_FULL: Spool Capacity Reached SPOOL_FULL --> SPOOL_TRANSMITTING: Communication Restored SPOOL_FULL --> SPOOL_INACTIVE: Spool Purged

3. State Definitions

State Description
SPOOL INACTIVE Normal operation. Messages are sent directly to host.
SPOOL ACTIVE Communication lost. Messages are being stored in spool.
SPOOL FULL Spool has reached capacity. Oldest messages may be overwritten.
SPOOL TRANSMITTING Spooled messages are being transmitted to host.

4. Transition Table

# Current State Trigger Next State Action
1 SPOOL INACTIVE Communication failure SPOOL ACTIVE Begin spooling messages
2 SPOOL INACTIVE Host requests spool (S2F43) SPOOL INACTIVE Configure spool streams
3 SPOOL ACTIVE Communication restored SPOOL TRANSMITTING Begin transmitting spool
4 SPOOL ACTIVE Capacity reached SPOOL FULL Handle overflow
5 SPOOL ACTIVE Spool disabled/purged SPOOL INACTIVE Clear spool
6 SPOOL FULL Communication restored SPOOL TRANSMITTING Begin transmitting spool
7 SPOOL FULL Spool purged SPOOL INACTIVE Clear spool
8 SPOOL TRANSMITTING All messages sent SPOOL INACTIVE Resume normal operation
9 SPOOL TRANSMITTING Communication lost SPOOL ACTIVE Continue spooling

5. Spooling Configuration

5.1 Spoolable Streams

Stream Function Spool Notes
S5 Alarm Messages Yes All alarm events spooled
S6 Collection Events Yes Event reports spooled
S6 Trace Data [Yes/No] Trace reports (configurable)

5.2 Spool Parameters

Parameter Value Description
Max Spool Size [10000] messages Maximum messages in spool
Overflow Action [Overwrite Oldest / Reject New] Action when spool full
Spool Streams S5, S6 Streams to spool
Message Direction Description
S2F43 H→E Define Spool Streams
S2F44 E→H Define Spool Acknowledge
S6F23 E→H Request Spooled Data
S6F24 H→E Spooled Data Request Grant

6.1 S2F43 - Define Spool Streams

Structure: 

S2F43 W
<L[n]
  <L[2]
    <STRID>           // Stream ID
    <STSPM>           // Spool flag (0=off, 1=on, 2=purge)
  >
  ...
>

6.2 S2F44 - Define Spool Acknowledge

Structure: 

S2F44
<L[n]
  <L[2]
    <STRID>           // Stream ID
    <STSPACK>         // Acknowledge code
  >
  ...
>

STSPACK Values:

Value Description
0 OK, spool defined
1 Stream not valid
2 Stream not supported for spooling

6.3 S6F23 - Request Spooled Data

When communication is restored, equipment may request permission to transmit spooled data:

Structure: 

S6F23 W
<RSDC>                // Request spool data count

6.4 S6F24 - Spooled Data Request Grant

Structure: 

S6F24
<RSDA>                // 0=Transmit, 1=Do not transmit, 2=Purge

7. Spool Transmission Sequence

sequenceDiagram participant Host participant Equipment Note over Equipment: Communication Restored Equipment->>Host: S6F23 (RSDC=150) Host-->>Equipment: S6F24 (RSDA=0, Transmit) Note over Equipment: Begin Spool Transmission loop For each spooled message Equipment->>Host: Spooled Message (S5F1, S6F11, etc.) Host-->>Equipment: Acknowledge end Equipment->>Host: S6F11 (SpoolTransmitComplete) Host-->>Equipment: S6F12 Note over Equipment: State: SPOOL INACTIVE
SVID Name Type Description
[4001] SpoolState U1 Current spooling state
[4002] SpoolCount U4 Number of messages in spool
[4003] SpoolCapacity U4 Maximum spool capacity
[4004] SpoolOverflowCount U4 Messages lost due to overflow

SpoolState Values:

Value State
0 SPOOL INACTIVE
1 SPOOL ACTIVE
2 SPOOL FULL
3 SPOOL TRANSMITTING
CEID Name Description
[4001] SpoolActivated Spooling started due to communication loss
[4002] SpoolFull Spool capacity reached
[4003] SpoolTransmitStart Beginning spool transmission
[4004] SpoolTransmitComplete All spooled messages transmitted
[4005] SpoolPurged Spool has been purged
ALID ALTX Category Description
[4001] Spool Overflow Warning Spool capacity reached, messages may be lost

11. Implementation Notes

11.1 Spool Storage

  • Spooled messages are stored in non-volatile memory
  • Messages are preserved across equipment restarts
  • FIFO ordering is maintained

11.2 Transmission Order

When transmitting spooled messages: 1. Messages are sent in chronological order (oldest first) 2. Equipment waits for acknowledgment before sending next message 3. If transmission fails, message remains in spool

11.3 Spool Purge

Spool can be purged by: - Host command (S2F43 with STSPM=2) - Operator action (if permitted) - Automatic purge on overflow (if configured)