Automationdirect.com DirectLOGIC DL205 Series User Manual page 202

Chapter 4: System Design and Configuration
Step 1: Identify Master Port # and Slave #
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The first Load (LD) instruction identifies the
communications port number on the network
master (DL250-1/260) and the address of the
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slave station. This instruction can address up to
99 Modbus slaves, or 90 DirectNET slaves. The
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format of the word is shown to the right. The
"F1" in the upper byte indicates the use of the
bottom port of the DL250-1/260 PLC, port
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number 2. The lower byte contains the slave
address number in BCD (01 to 99).
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Step 2: Load Number of Bytes to Transfer
The second Load (LD) instruction determines
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the number of bytes which will be transferred
between the master and slave in the subsequent
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WX or RX instruction. The value to be loaded is
in BCD format (decimal), from 1 to 128 bytes.
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The number of bytes specified also depends on
the type of data you want to obtain. For example, the DL205 Input points can be accessed by
V-memory locations or as X input locations. However, if you only want X0 – X27, you'll have
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to use the X input data type because the V-memory locations can only be accessed in 2-byte
increments. The following table shows the byte ranges for the various types of
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DirectLOGIC™. products.
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DL205/405 Memory
V-memory
T / C current value
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Inputs (X, SP)
Outputs (Y, C, Stage, T/C bits)
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Scratch Pad Memory
Diagnostic Status
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DL305 Memory
A
Data registers
T / C accumulator
B I/O, internal relays, shift register bits,
T/C bits, stage bits
Scratch Pad Memory
C
Diagnostic Status(5 word R/W)
D
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DL205 User Manual, 4th Edition, Rev. B
F 1 0
CPU bottom port (BCD)
Internal port (hex)
LD
KF101
1 2
Bits per unit
16
16
8
8
8
8
Bits per unit
8
16
1
8
16
1
Slave Address (BCD)
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# of bytes to transfer
LD
K128
Bytes
2
2
1
1
1
1
Bytes
1
2
1
2
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