Chapter 12  Troubleshooting 
12-11 
Description  Remedy 
16#2021 
The checksum of the command 
received is incorrect. 
1. Check whether there is noise, and retry the sending of 
the command. 
2. Check whether the slave operates normally. 
16#2022 
The format of the command used 
in MODRW does not conform to 
the ASCII format. 
Make sure that the format of the command conforms to 
the ASCII format. 
16#2023 
There is a communication 
timeout when MODRW is 
Check whether the slave operates normally, and whether 
the connection is normal. 
16#2024 
The setting value of the 
communication timeout is invalid. 
(SM120/SM103) 
1. Check the program and the related special data 
registers. 
2. Set the communication port parameter for the CPU 
module in HWCONFIG again. 
16#2025 
timeout when RS is executed. 
Check whether the slave operates normally, and whether 
the connection is normal. 
16#2026 
The RS communication interrupt 
Check whether the interrupt service routine used with RS 
16#2027 
The execution of FWD is 
Refer to AH500 Programming Manual, and check the 
16#2028 
The execution of REV is 
Refer to AH500 Programming Manual, and check the 
16#2029 
The execution of STOP is 
Refer to AH500 Programming Manual, and check the 
16#202A 
The execution of RSDT is 
Refer to AH500 Programming Manual, and check the 
16#202B 
The execution of RSTEF is 
abnormal. (SM102/103) 
Refer to AH500 Programming Manual, and check the 
instruction RSTEF. 
16#202C 
| 
I/O interrupt service routine   
0-31 does not exist. 
Download I/O interrupt service routine 0-31   
(I/O interrupt 0-31). 
| 
I/O interrupt service routine   
40-251 does not exist. 
Download I/O interrupt service routine 40-251   
(I/O interrupt 40-251). 
16#2128 
An action in a sequential function 
chart is incorrectly assigned 
qualifiers related to time. 
Check whether the action in the sequential function chart 
is assigned qualifiers related to time. 
16#2129 
The modifier R is assigned to an 
action in a sequential function 
chart incorrectly. (SM0/SM1) 
Check whether the reset modifier assigned to the action 
in the sequential function chart conflicts with another 
modifier assigned to the action in the sequential function 
16#212A 
MC/MCR instruction cannot be 
used in interrupt or subroutine. 
Check the program, compile the program again, and 
download the program again. 
16#6000 
Ethernet speed cannot be 
detected (SM1106) 
Check the Ethernet cable securely connected and is 
functioning normally.   
16#6001  Illegal IP address (SM1107) 
1. Check the program and the related special data 
registers. 
2. Set the Ethernet parameter for the CPU module in