Hello,

I have written a program for PIC16F688.
In this program I want to read in 152 Bytes via UART.

As it was not possible to define return_data: array[0..151] of Byte, i have splitted up the array into two:

return_data :array[0..79] of Byte;
return_data2 :array[0..71] of Byte;

I read in the data via UART and store 0 to 79 into return_data and 80 to 151 into return_data2

But the result is not correct. I guess this is because one variable is in a different bank.

During compilation I get the message: IRP must be set manually for indirect access to return_data2 variable
I have used in the code: setbit(status,IRP) in the main program without success.

What can I do to make it running?

many thanks
peter

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Regards Peter N.

Hi Peter,

To effectively control the IRP bit you have to know where your data arrays are in RAM. It's best to place them by yourself than to leave it to compiler, and to this purpose one may use the directive absolute. For example This will place return_data in Bank2 (requires IRP=1) and return_data2 in Bank1 (requires IRP=0 for indirect access). Thus Bank2 will be used up while there'll be some space left in Bank1 for the compiler to use.

Note that indirect access (requiring control of IRP) is used in statements like where compiler has to calculate RAM address depending on a variable, but not when the address may be estimated during compilation, like in

Here's an example how to clear your arrays

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Replacement libraries for mP PRO and PIC18 processors, mP PRO tips & trics

Hello,

thank you for your help.
With the absolute Statement and STATUS.IRP:=1; or :=0; it seems to work.

But I have two additional questions:


1) if you have a Statement like this:

if (return_value = $0A) AND (return_value2 = $23) then do something

how to handle this? (bringing the two array var first to some temp var?)



2) can you explain the statement return_data[idx]:=0; in more detail

if we assume the begining of the var array is stored in 0x120, what do I have to use for [idx] to access the 5th byte of the array?
Is it [id5]?

best regards
Peter

_________________
Regards Peter N.

ad 1) If array indexes are constant, like in then IRP bit is not involved. On the other hand, if the indexes are unknown at compile time then such conditional cannot work properly and has to be modified, for example
ad 2) idx is just a name of a variable (short for index) . To access the 5th byte of the array the variable has to have value of 4 (indexes start from 0).

Note that for the compileris equivalent to due to simple code optimization and thus the relevant memory byte will be accessed directly, regardless of IRP bit.

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Replacement libraries for mP PRO and PIC18 processors, mP PRO tips & trics