GE GFK-0804B manual Message Descriptions, Message 01 Read Output Table Format, Response

C

Message Descriptions

The following pages explain the format and fields for each RTU message.

Message (01): Read Output Table

Format:

Address Func 01

Starting Point No.

Number of

Points

Error Check

Hi Lo Hi Lo

Query

Address Func 01

Byte Count

Data

Error Check

Normal Response

Query:

HAn address of 0 is not allowed as this cannot be a broadcast request.

HThe function code is 01.

HThe starting point number is two bytes in length. It may be any value less than the highest output point number available in the Micro PLC. The starting point number is equal to one less than the number of the first output point returned in the normal response to this request.

HThe number of points value is two bytes in length. It specifies the number of output points returned in the normal response. The sum of the starting point value and the number of points value must be less than or equal to the highest output point number available in the Micro PLC. The high order byte of the starting point number and number of bytes fields is sent as the first byte. The low order byte is the second byte in each of these fields.

Response:

HThe byte count is a binary number from 1 to 256 (0 = 256). It is the number of bytes in the normal response following the byte count and preceding the error check.

HThe data field of the normal response is packed output status data. Each byte contains 8 output point values. The least significant bit (LSB) of the first byte contains the value of the output point whose number is equal to the starting point number plus one. The values of the output points are ordered by number starting with the LSB of the first byte of the data field and ending with the most significant bit (MSB) of the last byte of the data field. If the number of points is not a multiple of 8, then the last data byte contains zeros in one to seven of its highest order bits.

GFK±0804B Appendix C RTU Protocol C-9