IDEC MicroSmart - Manual (Page 412)

25: D ATA L INK C OMMUNICATION
25-4 « FC4A M ICRO S MART U SER ’ S M ANUAL »
Special Data Registers for Data Link Communication Error
In addition to data registers assigned for data communication, the master station has 31 special data registers and each
slave station has one special data register to store data link communication error codes. If any communication error occurs
in the data link system, communication error codes are set to a corresponding data register for link communication error at
the master station and to data register D8069 at the slave station. For details of link communication error codes, see below.
If a communication error occurs in the data link communication system, the data is resent two times. If the error still exists
after three attempts, then the error code is set to the data registers for data link communication error. Since the error code
is not communicated between the master and slave stations, error codes must be cleared individually.
Master Station
If any slave stations are not connected, master station data registers which are assigned to the vacant slave stations can be
used as ordinary data registers.
Slave Station
Note: Slave station data registers D8070 through D8099 can be used as ordinar y data registers.
Data Link Communication Error Code
The data link error code is stored in the special data register allocated to indicate a communication error in the data link
system. When this error occurs, special internal relay M8005 (data link communication error) is also turned on at both
master and slave stations. The detailed information of general errors can be viewed using
WindLDR . Select Online > Mon-
itor, then select Online > PLC Status > Error Status: Details. See page 29-2.
When more than one error is detected in the data link system, the total of error codes is indicated. For example, when
framing error (error code 2h) and BCC error (error code 10h) are found, error code 12h (18) is stored.
Special Data
Register
Data Link Communication Error Data
Special Data
Register
Data Link Communication Error Data
D8069 Slave station 1 communication error D8085 Slave station 17 communication error
D8070 Slave station 2 communication error D8086 Slave station 18 communication error
D8071 Slave station 3 communication error D8087 Slave station 19 communication error
D8072 Slave station 4 communication error D8088 Slave station 20 communication error
D8073 Slave station 5 communication error D8089 Slave station 21 communication error
D8074 Slave station 6 communication error D8090 Slave station 22 communication error
D8075 Slave station 7 communication error D8091 Slave station 23 communication error
D8076 Slave station 8 communication error D8092 Slave station 24 communication error
D8077 Slave station 9 communication error D8093 Slave station 25 communication error
D8078 Slave station 10 communication error D8094 Slave station 26 communication error
D8079 Slave station 11 communication error D8095 Slave station 27 communication error
D8080 Slave station 12 communication error D8096 Slave station 28 communication error
D8081 Slave station 13 communication error D8097 Slave station 29 communication error
D8082 Slave station 14 communication error D8098 Slave station 30 communication error
D8083 Slave station 15 communication error D8099 Slave station 31 communication error
D8084 Slave station 16 communication error — —
Special Data Register Data Link Communication Error Data
D8069 Slave station communication error
Error Code Error Details
1h (1) Overrun error (data is received when the receive data registers are full)
2h (2) Framing error (failure to detect star t or stop bit)
4h (4) Parity error (an error was found by the parity check)
8h (8) Receive timeout (line disconnection)
10h (16) BCC (block check character) error (disparity with data received up to BCC)
20h (32) Retr y cycle over (error occurred in all 3 trials of communication)
40h (64) I/O definition quantity error (discrepancy of transmit/receive station number or data quantity)