IDEC High Performance Series - Manual (Page 642)

Chapter 5
624
External Device Setup Manual
- FC2 Read discrete inputs - Reading of Input Relay (I) consecutively
Data sequence of read value
When two or more data are read out, the read data are arranged starting from the lowest address by 8 bits (1 byte). Within any 1
byte, data in the lower address is set to the lower bit. The data in the unread bit becomes “0”.
For example, when reading an 11-bit data as shown below, the read value becomes 21 03.
Address Data Remarks
C 1 1 Data for the 1st byte
Bit pattern= 00100001 = 21 (HEX) C 2 0
C 3 0
C 4 0
C 5 0
C 6 1
C 7 0
C 8 0
C 9 1 Data for 2nd byte
Bit pattern 00000011 = 03 (HEX) C 10 1
C11 0
Request
Byte 7 FC (Function code)=02
Byte 8-9 Reference No.
Byte 10-11 Number of read bits (1 to 2000 bits)
Normal response
Byte 7 FC (Function code)=02
Byte 8 Number of bytes for the response ((number of read bits+7)/8)
From Byte 9 Read data
Abnormal response
Byte 7 FC (Function code)=82 (HEX)
Byte 8 Exception code 01 or 02
Example
Reading of I100001. 1 bit. The read value is 1.
02 00 00 00 01 => 02 01 01