167
CHAPTER 13 COMMUNICATIONS USING A RANDOM ACCESS BUFFER
13
13.5 Precautions when Creating Programs
13.5 Precautions when Creating Programs
This section describes the precautions when creating programs for communications using a random access buffer.
(1) Completion of the initial and open processes
The initial process and the connection open process need to be completed.
(2) Send request from a CPU module
A CPU module cannot issue send requests. In addition, reception completion in a CPU module is not confirmed.
When it is necessary to synchronize data sending/receiving between the CPU module and the connected device,
use communications using a fixed buffer.
(3) Random access buffer address
The address specified by the connected device and the address specified using the FROM/TO instructions are
different. For details, refer to the physical and logical addresses of a random access buffer. ( Page 167,
Section 13.6)
13.6 Physical and Logical Addresses of a Random Access
Buffer
This section describes the start address of the E71 random access buffer (without battery backup), which is specified
in commands.
Note that when designating the start address of a random access buffer, the address specified by a connected device
is different from that specified using the FROM/TO instructions.
• Physical address: Address specified with the FROM/TO instructions of a program
• Logical address: Address specified by a connected device as the start address in the command
Buffer memory areas
Fixed buffer
Random access
buffer
Logical address
0
H
( 0)
267F
H
( 9855)
2680
H
( 9856)
3E7F
H
(15999)
680
H
( 1664)
17FF
H
(6143)
Physical address
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