Emerson PNC001-A Series User Manual

PACSystems™ RX3i and RSTi-EP CPU Reference Manual Section 6
GFK-2222AK October 2019
Serial I/O, SNP & RTU Protocols 186
6.3.3.14 Message (67): Read Scratch Pad Memory
6.3.3.14.1 Format:
Figure 34: RTU Read Scratch Pad Memory Message Format
Address
Starting
Byte No.
Number of
Bytes
Error
Check
Func
67
Query
Address
Data
Error
Check
Func
67
Normal Response
Byte
Count
6.3.3.14.2 Query:
▪ An Address of 0 is not allowed as this cannot be a broadcast request.
▪ The Function Code is equal to 67.
▪ The Starting Byte Number is two bytes in length and may be any value less than or
equal to the highest scratch pad memory address available in the attached CPU as
indicated in the table below. The Starting Byte Number is equal to the address of the
first scratch pad memory byte returned in the normal response to this request.
▪ The Number of Bytes value is two bytes in length. It specifies the number of scratch
pad memory locations (bytes) returned in the normal response. The sum of the
Starting Byte Number and the Number of Bytes values must be less than two plus the
highest scratch pad memory address available in the attached CPU. The high order
byte of the Starting Byte Number and Number of Bytes fields is sent as the first byte
in each of these fields. The low order byte is the second byte in each of the fields.
6.3.3.14.3 Response:
▪ The Byte Count is a binary number from 1 to 256 (0 = 256). It is the number of bytes
in the Data field of the normal response.
▪ The Data field contains the contents of the scratch pad memory requested by the
query. The scratch pad memory bytes are sent in order of address. The contents of
the scratch pad memory byte whose address is equal to the Starting Byte Number is
sent in the first byte of the Data field. The contents of the scratch pad memory byte
whose address is equal to one less than the sum of the starting byte number and
number of bytes values is sent in the last byte of the Data field.

Emerson PNC001-A Series Specifications

General

Brand	Emerson
Model	PNC001-A Series
Category	Controller
Language	English