STEP 5 Version 6.6 MANUAL C79000-G8576-C820-01
3.4.4 Force Variables
This online function allows you to modify process variables and
to intervene directly in the process. Before you force variables,
you should consider the reaction of the process to your
intervention!
– The variables I, Q, F, S, T, C, D can be modified. The PG
influences the variables I, Q and F only in bytes or words
in the process image.
With the variables T and C in the format KM and KH, the
forcing of edge flags must be taken into account.
– The function can be executed in the STOP and RUN
modes of the programmable controller.
– The signal status display is stopped if an incorrect format
or operand is found.
– STEP 5 displays the message “forcing not possible”.
– Since STEP 5 modifications are made in bytes, variables
cannot be modified en bloc.

手册上还有一个表：
You can enter the following operands in the operand list:
Operand Permitted data formats
………………………………………………………………
F/Q/I/S KM
FY/QB/IB/SY KH (KM, KY, KS, KF)
FW/QW/IW/SW KH (KM, KY, KS, KF)
T KT (KM, KH)
C KC1) (KM, KY, KS, KF)
DW/DL1)/DR1) KH (KM, KY, KS, KF)
DB –
FD/QD/ID/DD/SD KH (KG, KY, KS)
–Symbol Dependent on operand type
………………………………………………………………………………
1) These operands and formats can only be seen (not
controlled).

（The variables I, Q, F, S, T, C, D can be modified. The PG
influences the variables I, Q and F only in bytes or words
in the process image）
好像输入字节(IB65)可以强制位的，输入字节的单个位单独时不能强制，只能查看状态值，我试单个位时强制（比如I65.4)，会有提示框提示强制不可能（message:force fct. not possible)

如果输入都不能强制还怎么搞啊