Mitsubishi Electric FR-CC2-N Series Instruction Manual page 127

• Content of normal response
Message
c Starting address
d No. of points
 Example) Read the successful register start address and number of successful accesses from
slave address 25 (H19).
Query message
Slave address
H19 H46
(8 bits) (8 bits)
Normal response (Response message)
Slave address
H19
(8 bits)
The number of holding registers that were successfully accessed was returned as two with the start address 41075 (Pr.75).
 Error response
• An error response is returned if the query message received from the master contains an illegal function, address or data.
No response is returned for parity, CRC, overrun, framing, and busy errors.
NOTE
• No response is also returned in the case of broadcast communication.
• Error response (Response message)
a. Slave address
H80 + Function
(8 bits)
(8 bits)
Message
a Slave address
b Function
c Exception code
• Error code list
Code Error item
01 ILLEGAL FUNCTION
02
ILLEGAL DATA ADDRESS
03 ILLEGAL DATA VALUE
*1 An error response is not returned in the following cases:
(a) Function code H03 (reading data of holding registers)
When the number of registers is specified as one or more and there are one or more holding registers from which data can be read
(b) Function code H10 (writing data to multiple holding registers)
When the number of registers is specified as one or more and there are one or more holding registers to which data can be written.
In other words, when function code H03 or H10 is used and multiple holding registers are accessed, an error response is not returned even if a
nonexistent holding register or holding register that cannot be read or written from/to is accessed.
NOTE
• An error response is returned if none of the accessed holding registers exist. When an accessed holding register does not
exist, the read value is 0 and the written data is invalid.
126
5. PARAMETERS
5.7 (N) Communication operation parameters
The start address of the holding register that was successfully accessed is returned.
Starting address = start register address (decimal) - 40001
For example, when starting address 0001 is returned, the holding register address that was
successfully accessed is 40002.
The number of holding registers that were successfully accessed is returned.
Function CRC check
— —
(8 bits) (8 bits)
Function Starting address
H46 H04
(8 bits) (8 bits)
b. Function c. Exception code
(8 bits)
Set the address received from the master.
The function code requested by the master and H80 is set.
The codes in the following table are set.
The query message from the master has a function code that cannot be handled by the slave.
The query message from the master has a register address that cannot be handled by the slave.
*1
(No parameter, parameter cannot be read, parameter cannot be written)
The query message from the master has data that cannot be handled by the slave.
(Out of parameter write range, a mode is specified, or other error)
Description
No. of points
H32 H00
(8 bits) (8 bits)
CRC check
L H
(8 bits) (8 bits)
Description
Error description
CRC check
H02 —
(8 bits) (8 bits)
—
(8 bits)