ProSoft Technology MVI56-AFC - Manual (Page 103)

MVI56-AFC ♦ ControlLogix Platform Archives
Liquid and Gas Flow Computer User Manual
ProSoft Technology, Inc. Page 103 of 316
February 25, 2011
The Selected Archive start address can be calculated as (assumes meters are
numbered starting at 1):
Daily Archive Start Address = 60000 + ((Meter Number -1) * 100)
Hourly Archive Start Address = 60000 + (((Meter Number -1) * 100) + 50)
Note: When using processor logic to retrieve extended archives, when possible, use unsigned 16-
bit integer data type variables to hold archive addresses. Unsigned 16-bit integers display data in
the range 0 to 65535.
If your programming software (such as Rockwell Automation
® RSLogix™5000) does not support
unsigned integer data types, there are a couple of possible alternatives. If your programming
software supports signed 32-bit double integer data types, you may use that type of variable to
hold the addresses above.
If you must use signed 16-bit integer data type variables to contain addresses (such as in the case
of Rockwell Automation RSLogix5 or RSLogix500), you will not be able to enter the values in the
previous table as positive numbers. This is because 16-bit signed integers display values only in
the range -32768 to +32767. But, it is the underlying bit pattern and not the displayed decimal
value that is important to the AFC module.
To enter the correct bit pattern for these addresses into a signed 16-bit integer, you will need to
enter them as negative numbers. To determine the correct negative number, simply subtract 65536
from the address in the table, which will result in a negative number being displayed in the signed
integer variable. This negative number (a binary twos-compliment form of the archive address) will
contain the equivalent bit pattern for the value in the chart if it were held in an unsigned integer
variable.
Use these modified versions of the above formulas to calculate the address values for signed 16-
bit integer variables:
Daily Archive Start Address = ((60000 + ((Meter Number -1) * 100)) - 65536)
Hourly Archive Start Address = ((60000 + (((Meter Number -1) * 100) + 50)) - 65536)