Hitachi EH-150 Series Applications Manual page 89

(2) The state of receiving data area
1) Completed properly
When performance is properly, completion flag (t+1) will be ON, and nothing is stored in receiving data area. A
properly execution code is stored in a return code (s+0).
2) Receiving exception response
When an exception response is received, error flag (t+2) turns on, and the receiving data area is as follows.
Figure 6.46 Receiving data area format (Function code 0x0F / Exception response)
3) Other errors (except for exception response)
When there is no response from a slave or an abnormal factor is detected in the response, error flag (t+2) turns on,
an error code is stored in the return code area of the s parameter, and the number of receiving data is cleared to
H0000. (Data other than the number of receive data bytes maintains previous values.)
Please refer to section "6.3.5 Error detection in modbus master mode" for more information on error codes.
Number of receive data (H0002)
H 8 F Exception code
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Chapter 6 Communication Mode