FieldServer FS-8700-78 Computer Drive User Manual


 
Driver Manual
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6.4 Writing 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.