Chapter 6 Task Code Communication 6-1 To; H Series Communication Specification; Outline - Hitachi HIDIC EH-150 Applications Manual

Chapter 6
H series PLC has a communication protocol called task code, which enables easy communication between
host computer and EH-ETH.
Features of task code communication
- No need ladder program for task code communication.
- A Host computer is able to up/download a ladder program to/from a CPU module using the task code.
Also, it is possible to write and read any data in CPU module.
- EH-ETH transmits the request task code to EH-CPU448 to omit the header information of TCP (or UDP)
packet issued by a host computer. This to, EH-ETH transmit response task code to a host computer to add
TCP (or UDP) packet header information.
6.1

H series communication specification

The detailed function of each task code(command) is described in this chapter.
6.1.1

Outline

The following shows the outline of H series communication specification.
Logical layer
Data link layer
Physical layer
Module name
EH-ETH use uni-directional procedure at data link layer. At this uni-directional procedure, only a host
computer can start the communication to H series module. The task code communication supported by EH-
ETH is passive protocol because EH-ETH can respond only.
As explained above, for H-series, the protocol is defied so that the host computer can access all CPU in the
network of H-series.
The following five functions of H-series are available to users.
(1) CPU control
(2) I/O control
(3) Read memory
(4) Write memory
(5) Response
To utilize these functions, various task codes are to be assembled in the host computer program.
See the EH-150 application manual (NJI-280*(X)) Appendix 3 Task Code Specifications for detailed task
code (command code). And see the next chapter for data format.
Task code communication
Functions viewed from user7s eyes
I/Control CPU control memory read/write response
Combination of task codes
Protocol for each task code
TCP/IP, UDP/IP
IEEE 802.3
EH-ETH
Figure 6.1.1 Out line of the communication protocols for H series
: RUN/STOP control of CPU, set/reset of occupancy, Read CPU status etc.
: Various monitors
: Read programs etc.
: Clear all, transfer all etc,
: Various response from CPU
Chapter 6 Task code communication
Communication procedure 1,2
RS-232C, RS-422, RS-485
EH-CPU448
6-1