4-187 Detailed explanation of command words
4MELFA-BASIC IV
[Explanation]
(1) An input signal is read when referencing this variable.
(2) An output signal is written when assigning a value to this variable.
(3) It is not allowed to reference an output signal by this variable. Use the M_Out variable in order to refer-
ence an output signal.
(4) The variable name can have up to eight characters. Refer to the Page 129, "4.3.6 Types of characters
that can be used in program" for the characters that can be used.
(5) When mask information is designated, only the specified signal will be validated.
Example) In the above example on the 20th step, the input/output data with a bit width of eight is masked
by 0F in hexadecimal. Thus, if PORT 2 is used thereafter,
•When used as an input signal (M1 = PORT 2):
Numbers 5 to 8 are used for input, and numbers 9 to 12 are always treated as 0.
No. 12 No.5 (Input/output bit No.)
0000 1111
Invalid Valid
•When used as an output signal (PORT 2 = M1):
Data to be output this time is output to numbers 5 to 8, and the status currently being output is retained at
numbers 9 to 12.
No. 12 No.5 (Input/output bit No.)
****
1111
| |
Retains the current output status Output data of this time
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