> For the complete documentation index, see [llms.txt](https://support.powerio.com/hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.powerio.com/hub/codesys-hvac/en/hvac-modbus-library/functionblocks/systemair/systemair_access_control.md). # SYSTEMAIR\_ACCESS\_CONTROL ## `SYSTEMAIR_ACCESS_CONTROL` (FB) `FUNCTION_BLOCK` SYSTEMAIR\_ACCESS\_CONTROL ### Representation
InOut: | Scope | Name | Type | Initial | Comment | | ----------- | -------------------- | --------------------------------------------- | ------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- | | Input | `xEn` | `BOOL` | TRUE | Enable / disable communication (TRUE = enable) | | Input | `byUnitId` | `BYTE` | 0 | Address of the device | | Input | `xUpdateActual` | `BOOL` | FALSE |

Update of actual values (on every rising edge
)

| | Input | `xUpdateSetp` | `BOOL` | FALSE |

Update of setpoints (on every rising edge
)

| | Input | `eExternalCon` | SYSTEMAIR\_ACCESS\_CONTROL\_EXTERNAL\_CONTROL | SYSTEMAIR\_ACCESS\_CONTROL\_EXTERNAL\_CONTROL.NO\_EXTERNAL\_CONTROL | External control of the unit — default | | Input | `eTempConMode` | SYSTEMAIR\_ACCESS\_CONTROL\_TEMP\_CONTR\_MODE | SYSTEMAIR\_ACCESS\_CONTROL\_TEMP\_CONTR\_MODE.SUPPLY\_AIR | Type of temperature control of the unit — default | | Input | `eFanConMode` | SYSTEMAIR\_ACCESS\_CONTROL\_FAN\_CONT\_MODE | SYSTEMAIR\_ACCESS\_CONTROL\_FAN\_CONT\_MODE.FLOW | Type of fan control of the unit — default | | Input | `rSpTempSupplyAir` | `REAL` | 21.0 |

Supply air setpoint temperature in degrees Celsius when eTempConMode =
SYSTEMAIR\_ACCESS\_CONTROL\_TEMP\_CONTR\_MODE.SUPPLY\_AIR

| | Input | `rSpTempExtrAir` | `REAL` | 22.0 |

Exhaust air setpoint temperature in degrees Celsius when eTempConMode =
SYSTEMAIR\_ACCESS\_CONTROL\_TEMP\_CONTR\_MODE.EXTRACT\_AIR\_CASCADE

| | Input | `rSpTempRoom` | `REAL` | 22.0 |

Room setpoint temperature in degrees Celsius when eTempConMode =
SYSTEMAIR\_ACCESS\_CONTROL\_TEMP\_CONTR\_MODE.ROOM\_CASCADE

| | Input | `xAckAlarmsDev` | `BOOL` | FALSE | Acknowledge all alarms (TRUE = active) | | Input | `xResAlarmSICDev` | `BOOL` | FALSE |

Reset of the service interval counter alarm (TRUE
= active)

| | Input | `xResError` | `BOOL` | FALSE |

Reinitialization of the output eErrorCodeCom on the
error-free state (on each rising edge)

| | Inout | `ModbusClient` | `ModbusClientBase` | | Client of the device | | Output | `eUnitModeFb` | SYSTEMAIR\_ACCESS\_CONTROL\_OP\_MODE\_FB | | Device operating mode — feedback | | Output | `eUnitTrigFb` | SYSTEMAIR\_ACCESS\_CONTROL\_TRIG\_FB | |

Cause of the current operating mode of the unit —
feedback

| | Output | `eExternalConFB` | SYSTEMAIR\_ACCESS\_CONTROL\_EXTERNAL\_CONTROL | | State of the external control of the unit — feedback | | Output | `eTempConModeFB` | SYSTEMAIR\_ACCESS\_CONTROL\_TEMP\_CONTR\_MODE | |

Current type of temperature control of the unit —
feedback

| | Output | `eFanConModeFB` | SYSTEMAIR\_ACCESS\_CONTROL\_FAN\_CONT\_MODE | |

Current type of fan control of the unit —
feedback

| | Output | `eSupAirFanMode` | SYSTEMAIR\_ACCESS\_CONTROL\_FAN\_MODE | | Operating mode of the supply air fan | | Output | `eExtAirFanMode` | SYSTEMAIR\_ACCESS\_CONTROL\_FAN\_MODE | | Operating mode of the exhaust air fan | | Output | `rTempOda` | `REAL` | | Current outside temperature in degrees Celsius | | Output | `rTempIntakeAir` | `REAL` | | Current outside air temperature in degrees Celsius | | Output | `rTempSupplyAir` | `REAL` | | Current supply air temperature in degrees Celsius | | Output | `rTempExhaustAir` | `REAL` | | Current exhaust air temperature in degrees Celsius | | Output | `rTempExtractAir` | `REAL` | | Current extract air temperature in degrees Celsius | | Output | `rSupplyAirPres` | `REAL` | | Current pressure in the supply air in Pa | | Output | `rExtractAirPres` | `REAL` | | Current pressure in the extract air in Pa | | Output | `rSupplyAirFlow` | `REAL` | | Current volume flow in the supply air | | Output | `rExtractAirFlow` | `REAL` | | Current volume flow in the extract air | | Output | `rExtractAirCO2` | `REAL` | | Current CO2 content in the extract air / room in ppm | | Output | `rExtractAirHum` | `REAL` | |

Current relative humidity in the extract air / room in
percent

| | Output | `rFilterSupAir` | `REAL` | | Differential pressure - filter - supply air in Pa | | Output | `rFilterExtAir` | `REAL` | | Differential pressure - filter - extract air in Pa | | Output | `rTempAveragRoom` | `REAL` | |

Temperature - average of all four room temperature sensors in
degrees Celsius

| | Output | `rActiveSeq` | `REAL` | | Number of the active sequence (1 … 10) | | Output | `arrContSigSeq` | `ARRAY` \[1 .. 10] `OF` `REAL` | | Control signal of the individual sequences (1 … 10) | | Output | `rSupAirFanCon` | `REAL` | | Control signal for the supply air fan in percent | | Output | `rExtAirFanCon` | `REAL` | | Control signal for the exhaust air fan in percent | | Output | `rSpTempSupplyAirFb` | `REAL` | |

Current setpoint of the supply air temperature in degrees Celsius —
feedback

| | Output | `rSpSupAirFan` | `REAL` | |

Current setpoint for the supply air fan as pressure /
volume flow

| | Output | `rSpExtAirFan` | `REAL` | |

Current setpoint for the exhaust air fan as pressure /
volume flow

| | Output | `rSFP` | `REAL` | | Specific fan power in Ws/m3 | | Output | `rSupAirFanUpM` | `REAL` | | Number of revolutions of the supply air fan per minute | | Output | `rExtAirFanUpM` | `REAL` | | Number of revolutions of the exhaust air fan per minute | | Output | `rPosDamper_1` | `REAL` | | Current position of damper 1 in percent | | Output | `rPosDamper_2` | `REAL` | | Current position of damper 2 in percent | | Output | `rPosDamper_3` | `REAL` | | Current position of damper 3 in percent | | Output | `rPosDamper_4` | `REAL` | | Current position of damper 4 in percent | | Output | `rPosDamper_5` | `REAL` | | Current position of damper 5 in percent | | Output | `rSpSupAirCool` | `REAL` | | Setpoint - supply air temperature in cooling mode in degrees Celsius | | Output | `rSpSupAirHeat` | `REAL` | | Setpoint - supply air temperature in heating mode in degrees Celsius | | Output | `rSpDehum` | `REAL` | | Setpoint - dehumidification in percent relative humidity | | Output | `rSpHum` | `REAL` | | Setpoint - humidification in percent relative humidity | | Output | `eHumConMode` | SYSTEMAIR\_ACCESS\_CONTROL\_HUM\_MODE | | Current operating mode for humidification / dehumidification | | Output | `xErrorDevice_A` | `BOOL` | |

Alarm output - unacknowledged fault messages - Alarm A (
TRUE = fault active)

| | Output | `xErrorDevice_B` | `BOOL` | |

Alarm output - unacknowledged fault messages - Alarm B (
TRUE = fault active)

| | Output | `xErrorDevice_C` | `BOOL` | |

Alarm output - unacknowledged fault messages - Alarm C (
TRUE = fault active)

| | Output | `xFilterSupAir` | `BOOL` | |

Filter maintenance indicator - supply air (TRUE = maintenance required
)

| | Output | `xFilterExtAir` | `BOOL` | |

Filter maintenance indicator - extract air (TRUE = maintenance required
)

| | Output | `xFireAlarm` | `BOOL` | | Fire alarm (TRUE = alarm active) | | Output | `xSmokeAlarm` | `BOOL` | | Smoke alarm (TRUE = alarm active) | | Output | `xAlarm` | `BOOL` | FALSE | Collective fault (TRUE = fault) | | Output | `xAlarmCom` | `BOOL` | FALSE | Collective fault - communication (TRUE = fault) | | Output | `eErrorCodeCom` | ModbusErrorCode | | Error code - communication (0 = no error) | | Output | `xBusy` | `BOOL` | | Communication indicator (TRUE = communication) | | Input Const | `diAdrOffset` | `DINT` | 0 |

Offset for calculating the Modbus addresses (from the Modbus
registers) (permitted range: -1, 0, +1)

| | Input Const | `tTimeUpdateSetp` | `TIME` | TIME#45s0ms |

Update interval for the operations that are influenced by the input
xUpdateSetp influenced

| | Input Const | `tTimeUpdateActual` | `TIME` | TIME#10s0ms |

Update interval for the operations that are influenced by the input
xUpdateActual influenced

| --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://support.powerio.com/hub/codesys-hvac/en/hvac-modbus-library/functionblocks/systemair/systemair_access_control.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.