FieldServer FS-8700-78 instruction manual Writing data to Dap Devices, Driver Manual

Driver Manual

6.4Writing data to Dap Devices

The variables in a DAP device are not individually addressable . When a DAP device is read a data composite is returned. The driver extracts the data you require. When data is written to a DAP device it is not possible to write a value to one individual data element such as a temperature setpoint. Rather, the DAP devices requires the complete data composite (all its variables, states, settings) be written at once. This makes the setting of a setpoint a complex operation for the driver.

It involves the following steps

i.Read the device, obtain a complete set of data and store (internally in the driver.).

ii.Use this stored data to form the basis for a write. Modify the data with the data the user wishes to set.

iii.Write the modified data composite back to the DAP device.

You can see that to complete a 'write' operation successfully, we must first read the device successfully. If the read has not been completed then the write operation will be abandoned. The driver prints messages to the error logs and records a NODE_OFFLINE stat each time that it attempts to write but is unable to.

The DAP-Config command is an exception to the above notes. A read is not required. The Dap Config command is used to turn off/on DAP units. The Command uses two consecutive array elements. The first is the zone, the second is the inhibit command. Valid zones are 0-63.

If any inhibit bit (bits 0-5) is set then the unit will not run. If bits 0 to 5 are off then the unit will run. Bits 6& 7 are used for display only on the DAP panel.

0x01 - Inhibit Cooling

0x02 - Inhibit Heating

0x04 - Inhibit Humid

0x08 - Inhibit Dehumidification

0x10 - Inhibit fan

0x20 - Reserved

0x40 - Network Standby - Display on panel (only has no effect on unit) 0x80 - Network off inhibit is active - display only - no effect on operation

This function should be used as a wrbc/x. When the driver encounters this command it reads the associated data array, loads the two elements found at the array offset into the message and transmits the message. The driver does not set any data array elements to confirm that the command concluded successfully.

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