Table of Contents
Advertisement
APPENDIX
Appendix 7.2 Control by Signals
Appendix 7.2.1 ER (DTR) control enabled
(BASIC program)
ZOPEN • • • •
ZRECEIVE • • • •
Data
reception result
ZRECEIVE • • • •
Data
reception result
ZRECEIVE • • • •
Data
reception result
ZCLOSE
App - 28
The following diagram shows the data flow when control by signals is enabled in the
communication channel.
When the ER (DTR) control is enabled, ER (DTR) control signals of the RS-232C
interface are turned ON/OFF based on the size of the free area in the receive buffer
specified by the user, allowing the data transmission from the external device to the
communication module to be controlled and requested.
An ER control signal is turned OFF when the free area in the receive buffer becomes
one-fourth or less of the total space as data received from the external device is
stored.
An ER control signal is turned ON when the free area in the receive buffer becomes
three-fourths or more of the total space because of receive requests from the BASIC
program in the communication module.
A
D51H
Channel open
1
Receive buffer
The free area is
one-fourth or less.
The free area is
three-fourths or more.
3
Communication module
(OS)
ER control
signal
Data
ER control
signal
2
ER control
signal
Data
MELSEC-Q
ON
External device
OFF
ON
App - 28
Advertisement
Table of Contents
