Mitsubishi MELSEC Q Series, Programming Manual

Page: 486 / 816

7-146
7.10 Debug/Error Diagnostics Instructions
7.10.1 Special format error check
CHKST, CHK
(7) Place LD and AND instructions prior to the CHK instruction to establish a check condition.
Check conditions cannot be set using other contact instructions.
If a check condition has been set with the LDI or ANI instruction, the processing for the
check condition they specify will not be performed.
However, contact numbers during error detection can also be assigned to the LDI and ANI
instructions.
(8) The error detection method differs according to whether SM710 is ON or OFF.
(a) If SM710 is OFF, checks are performed on coil numbers 1 through 6 in order of contact
number.
When the CHK instruction is executed, checks are performed on coils of contact No.1 in
order from coil No.1 through coil No.6, then move on to contact No. 2 and check the
coils in order from coil No.1 through coil No.6.
The CHK instruction is completed when coil No. 6 of contact No. n is checked.
(b) If SM710 is ON, checks are performed on contact numbers 1 through n in order of coil
number.
When the CHK instruction is executed, checks are performed on the ladder with coil No.
1 in order from contact No. 1 through contact No. n, then move on to the ladder with coil
No. 2 and checks the ladder in order from contact No. 1 through contact No. n.
The CHK instruction is completed when contact No. n of coil No. 6 is checked.
(9) If more than one error is detected, the number of the first error detected is stored.
Error numbers detected after this are ignored.
(10) The CHK instruction cannot be used in a low speed execution type program.
If a low speed execution type program is set in a program file containing the CHK
instruction, an operation error is returned, and the CPU module operation is suspended.
O peration Error
In any of the following cases, an operation error occurs, the error flag (SM0) is turned ON, and
the corresponding error code is stored to SD0.
• There is a parallel ladder. (Error code: 4235)
• There are more than 150 contact instructions. (Error code: 4235)
• The CHK instruction is not executed following the CHKST instruction.
(Error code: 4235)
• The CHK instruction is executed when no CHKST instruction has been executed.
(Error code: 4235)
• The CHKST and CHK instructions are used in a low speed execution type program.
(Error code: 4235)
• There is a instruction other than the LD, LDI, AND or ANI instruction between the CHK
instruction and the CHKST instruction. (Error code: 4235)
• The CHK instruction is used at three places or more in all program files being executed.
(Error code: 4235)
• The CHK instruction is used at two places or more in a single program file.
(Error code: 4235)
X 5 X 7 X 9 X A
1 2 3 4 C ontact N o .
X 1A X 1C
CHK
EN ENO
C ontact num b ers are a ll ocate d
Does not execute chec k