Chapter 6. Serial I/O, SNP & RTU Protocols
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PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual
GFK-2222AD
Message (16): Preset Multiple Registers
Format:
Address
Number of
Registers
Error Check
Func
16
Query
Normal Response
Address
Error Check
Func
16
Byte
Count
Data
Starting
Register No.
Number of
Registers
Starting
Point
Figure 61: RTU Preset Multiple Registers Message Format
Query:
▪
An Address of 0 indicates a broadcast request. All slave stations process a broadcast re-quest and
no response is sent.
▪
The value of the Function code is 16.
▪
The Starting Register Number is two bytes in length. The Starting Register Number may be any value
less than the highest register number available in the attached CPU. It is equal to one less than the
number of the first register preset by this request.
▪
The Number of Registers value is two bytes in length. It must contain a value from 1 to 125 inclusive.
The sum of the Starting Register Number and the Number of Registers value must be less than or
equal to the highest register number available in the attached CPU. The high order byte of the
Starting Register Number and Number of Registers fields is sent as the first byte in each of these
fields. The low order byte is the second byte in each of these fields.
▪
The Byte Count field is one byte in length. It is a binary number from 2 to 250 inclusive. It is equal to
the number of bytes in the data field of the preset multiple registers request. Note that the Byte
Count is equal to twice the value of the Number of Registers.
▪
The registers are returned in the Data field in order of number with the lowest number register in
the first two bytes and the highest number register in the last two bytes of the Data field. The number
of the first register in the Data field is equal to the starting register number plus one. The high order
byte is sent before the low order byte of each register.
Response:
▪
The descriptions of the fields in the response are covered in the query description.
