Hitachi EH-150 Series - Basic Specification of Transmission Control Procedure

Appendix
A - 10
A.3.3 Basic specification of transmission control procedure
The communication sequence of a host and PLC is shown in the following figure.
Host
PLC
ACK
T
M
LUMP
Task
code
S
u
m
S
T
X
S
T
X
C
R
Res-
ponse
ENQ
1
The minimum cycle
In case of CPU “Busy”
EOT
ENQ
1
EOT
LUMP
C
R
Host
PLC
T
M
LUMP
Task
code
S
u
m
S
T
X
C
R
ACK
ENQ
1
ENQ
1
S
T
X
Res-
ponse
LUMP
C
R
Figure.A.5 Transmission control procedure 1 Communication sequence diagram
Host
PLC
T
M
Task code
S
u
m
S
T
X
S
T
X
C
R
Response
The minimum cycle
In case of CPU “Busy”
C
R
Host
PLC
T
M
Task code
S
u
m
S
T
X
C
R
S
T
X
Response
C
R
Figure.A.6 Transmission control procedure 2 Communication sequence diagram