CPU Specifications
and Operation
4–42
CPU Specifications and Operation
The first Load (LD) instruction identifies
the communications port number on the
network master (DL05) and the address of
the slave station. This instruction can
address up to 99 MODBUS slaves, or 90
DirectNET slaves. The format of the word
is shown to the right. The “F2” in the upper
byte indicates the use of the right port of
the DL05 PLC, port number 2. The lower
byte contains the slave address number in
BCD (01 to 99).
2 0 1F
Internal port (hex)
Port number (BCD)
Slave address (BCD)
LD
KF201
The second Load (LD) instruction
determines the number of bytes which will
be transferred between the master and
slave in the subsequent WX or RX
instruction. The value to be loaded is in
BCD format (decimal), from 1 to 128
bytes.
6 4
(BCD)
# of bytes to transfer
LD
K64
The number of bytes specified also depends on the type of data you want to obtain.
For example, the DL05 Input points can be accessed by V-memory locations or as X
input locations. However, if you only want X0 – X27, you’ll have 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
DirectLOGIC products.
DL 05 / 205 / 350 / 405 Memory Bits per unit Bytes
V memory
T / C current value
16
16
2
2
Inputs (X, SP) 8 1
Outputs
(Y, C, Stage, T/C bits)
8 1
Scratch Pad Memory 8 1
Diagnostic Status 8 1
DL330 / 340 Memory Bits per unit Bytes
Data registers
T / C accumulator
8
16
1
2
I/O, internal relays, shift register
bits, T/C bits, stage bits
1 1
Scratch Pad Memory 8 1
Diagnostic Status(5 word R/W) 16 10
Step 1:
Identify Master
Port # and Slave #
Step 2:
Load Number of
Bytes to Transfer
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