FieldServer FS-8700-80 - Manual (Page 24)

McQuay Micro Tech Open Protocol Driver Manual Page 24 of 43
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7.3.4 Map Descriptor Example – Strategy 1.
This example illustrates the configuration of the FieldServer as a McQuay Micro Tech Open Protocol Server where a single Map Descriptor is used to emulate a
McQuay device’s memory as one large single block of bytes. Any requests in the address range 1-0x270F can be serviced by this one Map Descriptor. Is has
the drawback that a large Data Array which will be mostly empty is used. This does not affect performance but uses the FieldServer’s memory resource.
When a poll is received, the driver looks through the Map Descriptor and finds one with a matching Node and one whose address and length cover the poll’s
address.
Map_Descriptor_Name , Data_Array_Name , Data_Array_Offset , Function , Node_Name , Address , Length
Chiller1_emulation
, DA_CHILLER1 , 0 , Passive , Chiller1 , 1 , 10000
7.3.5 Map Descriptor Example – Strategy 2.
In this example the memory being emulated is divided into chunks to avoid having a large sparse array. When a poll is received, the driver looks through the
Map Descriptors and finds one with a matching Node and one whose address and length cover the poll’s address.
Map_Descriptor_Name , Data_Array_Name , Data_Array_Offset , Function , Node_Name , Address , Length
Chiller1_emulation1 , DA_CHILLER1 , 0 , Passive , Chiller1 , 1024 , 256
Chiller1_emulation2 , DA_CHILLER1 , 256 , Passive , Chiller1 , 2048 , 256
Ensure that Data Array’s
length is at least as long as
the Map Descriptor’s.
A data format of BYTE is
appropriate. Passive means that the Map
Descriptor responds to polls but
does not generate any polls itself. The Node name connects the
Map Descriptor to a Node
definition and possibly to a port. 10, 000 is the maximum length of a
Data Array so there is no point in
making the Map Descriptor longer.
The same Data
Array is used for
both Map
Descriptors.
By using the same
Data Array and
changing the offset
the data can all be
packed into a
smaller array.
1024 = 0x400; 2048 = 0x800
These two address ranges cover almost all the data fields in a 200 series chiller.
A few more Map Descriptors could be added to serve the remaining data field
addresses.