What does the following lines of C source code mean?

[android5555]

1. Explain what the CPU will do in terms of functuality and configuration when executing the C source code below:

unsigned char value = 0x91

1) BSR = 5;

2) BSRbits.3 = 1;

3) INTCONbitsTMR0IE = 1;

4) INTCON2bitsTMR0IP = 1;

5) TRISB = 0x00;

6) PORTB = 0x00;


Please can somebody help me with this question.

 

[phinds]

you need to show some attempt on your own, else it doesn't really look like you are asking for "help" so much as just asking for the answer(s)

One thing I would say is that while it has been a long time since I've done any C programming, I don't think "BSRbits.3" is a valid C construct so on that one the CPU isn't likely to do anything at run-time because the compiler won't let it get that far.

 

[berkeman]

1. Explain what the CPU will do in terms of functuality and configuration when executing the C source code below:

unsigned char value = 0x91

1) BSR = 5;

2) BSRbits.3 = 1;

3) INTCONbitsTMR0IE = 1;

4) INTCON2bitsTMR0IP = 1;

5) TRISB = 0x00;

6) PORTB = 0x00;


Please can somebody help me with this question.

As phinds points out, you must show your attempt first, before we can offer tutorial help.

 

[rcgldr]

Looks like BSRbits is a structure or union with a bit field, but the syntax BSRbits.3 doesn't seem correct. It would help if you show the declaration for BSRbits (and the typedef if that is used).

 

[android5555]

I'm not sure if "BSRbits.3 = 1" is a valid C statement, but that is exactly what the question says. I think the "INTCONbitsTMR0IE = 1" statement means that the timer0 interrupt is enabled. From what i understand from "TRISB = 0x00" it should mean Port B is configured as outputs.

 

[CWatters]

I recommend you download a PIC data sheet and search it for relevant words like "INTCONbits", "TMR0IE", "PORTB" etc. There are also numerous guides on the web to the common bits of a PIC.

BSR stands for Bank Select Register. The BSR maps in banks of RAM and registers. See page 42..

http://ww1.microchip.com/downloads/en/devicedoc/30412c.pdf

Depending on the PIC..

The lower nibble is used to select the peripheral register bank. The upper nibble is used to select the general purpose memory bank.

 

[android5555]

Thanks i appreciate the help!

 

[HallsofIvy]

I thought that looked more like assembly language than C!