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

Chapter 6
H/EH series PLC has a communication protocol called task code, which enables easy communication
between host computer and EH-ETH2.
Features of task code communication
- No need user program for task code communication.
- A Host computer is able to up/download a user program to/from a CPU module using the task code. Also,
it is possible to write and read any data in CPU module.
- EH-ETH2 transmits the request task code to EH-CPU or EHV-CPU to omit the header information of TCP
(or UDP) packet issued by a host computer. This to, EH-ETH2 transmit response task code to a host
computer to add TCP (or UDP) packet header information.
6.1

H/EH 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/EH series communication specification.
Logical layer
Data link layer
Physical layer
Module name
Figure 6.1
EH-ETH2 use uni-directional procedure at data link layer. At this uni-directional procedure, only a host
computer can start the communication to H/EH series module. The task code communication supported by
EH-ETH2 is passive protocol because EH-ETH2 can respond only.
As explained above, for H/EH-series, the protocol is defied so that the host computer can access all CPU in
the network of H/EH-series.
The following five functions of H/EH-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 Appendix B Task Code Specifications for detailed task code (command code). And see the next
chapter for data format.
Task code communication
Functions viewed from user's eyes
I/O Control CPU control memory read/write response
Combination of task codes
Protocol for each task code
TCP/IP, UDP/IP
IEEE 802.3
EHV-CPU
EH-ETH2
Out line of the communication protocols for H/EH 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
supported EH-CPU
6-1