MemIn Function

Returns the status of the specified memory I/O port. Each port contains 8 memory bits.

Syntax
MemIn(portNumber)

Parameters

portNumber

Specify bytes of the memory I/O.

Return Values
Returns an integer value between 0 and 255. The return value is 8 bits, with each bit corresponding to 1 memory I/O bit.

Description
MemIn provides the ability to look at the value of 8 memory I/O bits at the same time. The MemIn instruction can be used to store the 8 memory I/O bit status into a variable or it can be used with the Wait instruction to Wait until a specific condition which involves more than 1 memory I/O bit is met.

Since 8 bits are retrieved at a time, the return value ranges from 0 and 255. Please review the chart below to see how the integer return values correspond to individual memory I/O bits.

Memory I/O Bit Result (Using Port #0)

Return Values	7	6	5	4	3	2	1	0
1	Off	Off	Off	Off	Off	Off	Off	On
5	Off	Off	Off	Off	Off	On	Off	On
15	Off	Off	Off	Off	On	On	On	On
255	On	On	On	On	On	On	On	On

Memory I/O Bit Result (Using Port #31)

Return Values	255	254	253	252	251	250	249	248
3	Off	Off	Off	Off	Off	Off	On	On
7	Off	Off	Off	Off	Off	On	On	On
32	Off	Off	On	Off	Off	Off	Off	Off
255	On	On	On	On	On	On	On	On

Note

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• Difference Between MemIn and MemSw

  The MemSw instruction allows the user to read the value of 1 memory I/O bit. The return value from MemSw is either a 1 or a 0 which indicates that the memory I/O bit is either On or Off. MemSw can check each of the memory I/O bits individually. The MemIn instruction is very similar to the MemSw instruction in that it also is used to check the status of the memory I/O bits. However there is 1 distinct difference. The MemIn instruction checks 8 memory I/O bits at a time vs. the single bit checking functionality of the MemSw instruction. MemIn returns a value between 0 and 255 which tells the user which of the 8 I/O bits are On and which are Off.

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See Also
In, InBCD, Off, MemOff, On, MemOn, OpBCD, Oport, Out, MemOut, Sw, MemSw, Wait

MemIn Function Example
The program example below gets the current value of the first 8 memory I/O bits and then makes sure that all 8 I/O are currently set to “0” before proceeding. If they are not “0” an error message is given to the operator and the task is stopped.

Function main
    Integer var1

    var1 = MemIn(0)  'Get the 1st 8 memory I/O bit value
    If var1 = 0 Then
        Go P1
        Go P2
    Else
        Print "Error in initialization!"
        Print "First 8 memory I/O bits were not all set to 0"
    EndIf
Fend

Other simple examples from the Command window are as follows:

> memout 0, 1
> print MemIn(0)
1
> memon 1
> print MemIn(0)
3
> memout 31,3
> print MemIn(31)
3
> memoff 249
> print MemIn(31)
1
>