Micromod Micro-DCI: 53SL5100A Single Loop Controller - Manual (Page 138)

Single Loop Process Controller Instruction Manual
130 Communications
B.1.5 Calculating Data Addresses
If communications software must be generated to accommodate unique Datalink applications require-
ments, then the instrument memory address scheme must be known for proper data bit (e.g., L data type)
and data byte (e.g., B, C, H, and A data types) memory location determination.
This memory address scheme applies only if a 6 is in memory address location 8002H. Memory address
location 8002H must be read and if it contains a 6, then the address scheme that is described in
Table B-3
should be applied for this instrument..
✎ Note
Numbers used in this section that are expressed in hexadecimal
notation (base 16) are identified with an H after the number.
Table B-3. Instrument Memory Address Scheme
Data
Type
Base
Memory
Address
Byte
Size
Data Format Address Calculation Algorithm
B 200H 1 Represents a positive integer with
values from 0 to 255. Address = B Base + (B Number)
= 200H + (B Number)
Address example: B012 location
= 200H + 12D = 200H + CH = 20CH
L 500H 1 Bit A single binary bit with a logical
value of 0 or 1. L datapoints are
packed 8 to a byte. Address = L Base + (L Number/8)
= 500H + (L Number/8)
Remainder = bit position in byte
Address example: L014 location =
500H + 14/8 = 501H, bit 6
(remainder).
C 600H 3 Represents floating point values
that have a resolution of one part in
32,768 (15 bits) and a dynamic
range of ± 10
38 . The first two bytes
represent a 2’s complement
notation in fractional form (2
-n
)
whose absolute value is between
0.5 and 0.9999. The third byte is the
power of 2 in 2’s complement
notation. Floating point example:
64H 00H 07H = 100D (Decimal)
64H = 0110 0100, fractional binary
weights left to right are
0 = 2’s complement positive,
1 = 2
-1
= 1/2 = 0.5, 1 = 2
-2
= 1/4 =
0.25, 0=0, 0=0, 1 = 2
-5
= 1/32 =
0.03125, 0=0, and 0=0.
64H = 0.5+0.25+0.03125 =
0.78125.07H = 128D. 128D X
0.78125D = 100.
Address = C Base + (3 X C Number)
= 600H + (3 X C Number)
Address example: C011 location
600H + (3 X 11) = 600H + 33D
= 600H + 21H = 621H.