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How to access the internal register (16f628a)

 
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neal1
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How to access the internal register (16f628a)
PostPosted: Tue Feb 24, 2009 11:23 am     Reply with quote
hi, I'm newbie here.....I just start using this ccs c compiler recently.
I wish to access SPBRG(99h) register and CMCON register and other registers.
Below is my code:
Code:

#include "F:\serial_port\test7\t7.h"
#include <ctype.h>
//do i need add any other .h file such as pic.h?
 //the t7.h is the default file that generate using PIC WIZARD n attached //at bottom

void main()
{

   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
   setup_timer_1(T1_DISABLED);
   setup_timer_2(T2_DISABLED,0,1);
   setup_comparator(NC_NC_NC_NC);
   setup_vref(FALSE);
   setup_oscillator(False);

   // TODO: USER CODE!!
SET_TRIS_A(00000000);
SET_TRIS_b(00000010);


//  i wish load some value into CMCON but not successfully
//  compiler said that it(CMCON) is not defined.
//CMCON = 0x07;
//0x07 is the value that i wish loaded into CMCON
}


//t7.h coding as below
/*
#include <16F648A.h>
#FUSES NOWDT, HS, NOPUT, NOPROTECT, BROWNOUT, MCLR, NOLVP, NOCPD
#use delay(clock=4000000)
#use rs232(baud=9600,parity=N,xmit=PIN_B2,rcv=PIN_B1,bits=8)
*/
Ttelmah
Guest
PostPosted: Tue Feb 24, 2009 11:28 am     Reply with quote
#byte CMCON=0x99

Then you can write to this register. There is a posted list here (a search for register name definitions, with 'search for all terms' selected, will find it), which can be loaded to give standard names for 99% of the registers.

However the reason it is not defined as standard, is that you don't need it.
If you have a #use RS232 statement, the compiler _automatically loads the register for you_. To change the setting, you can just use 'set_uart_speed(BAUD RATE);', and the compiler will calculate the value and load it for you.

Best Wishes
neal1
Guest
PostPosted: Tue Feb 24, 2009 12:09 pm     Reply with quote
hi Ttelmah,
u mean write like this way?

#byte CMCON=0x99; //define the CMCON at the 99h address
COMCON = 0x07;// load the value into it


and i would like to ask y my #use RS232 did not load the register for me? am i done any things wrong? or where i should put the " #use RS232 "? for this moment i put it at ".h" file
Ttelmah
Guest
PostPosted: Tue Feb 24, 2009 3:07 pm     Reply with quote
You show the four 'essential' lines remmed out in your t7.h file....
Get rid of the /* */ round these.

However there are then 'comments' about these. You are selecting 'HS', which is the oscillator fuse for more than 4MHz, but have the clock statement saying that your clock is 4MHz. You should be using either XT, if you have a 4MHz crystal, or set the clock statement to the right value, if you are using a faster crystal. HS is 'borderline', on some crystals at 4MHz. You have no power up timer selected, but generally operation is more reliable with PUT selected. You have the MCLR pin enabled, have you got a pull up on this?. You have brownout selected, but on these chips, the brownout is at a fixed 4v (nominal, and can be as high as 4.35v. This option _must not be selected_, if you are operating on anything below 5v....

If these options are correct, then removing the remarks from round these lines should make your chip work.

Best Wishes
treitmey



Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA

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PostPosted: Tue Feb 24, 2009 3:17 pm     Reply with quote
neal1
btw your #byte should NOT have a semicolon after it.
Quote:
#byte CMCON=0x99; //define the CMCON at the 99h address



Should be
Code:
#byte CMCON=0x99 //define the CMCON at the 99h address
neal1
Guest
PostPosted: Wed Feb 25, 2009 4:07 am     Reply with quote
i juz wan to double confirm that if i write
#byte CMCON=0x1f
this mean i define CMCON at 1fh right?
and this will be the same as the internal register in 16f628a right/?
meereck



Joined: 09 Nov 2006
Posts: 173

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PostPosted: Wed Feb 25, 2009 7:18 am     Reply with quote
neal1 wrote:
i juz wan to double confirm that if i write
#byte CMCON=0x1f
this mean i define CMCON at 1fh right?
and this will be the same as the internal register in 16f628a right/?

yes, you can access that register then.
Btw, you can also do something like this:
Code:
#byte CMCON=getenv("SFR:CMCON")

Which ensures that CMCON will always be appropriate regardless the target device.
neal1
Guest
PostPosted: Wed Feb 25, 2009 10:29 am     Reply with quote
erm....what if i just want to bit4 of certain register is HIGH or LOW? How i should set it?
eg:
I would like to set BIT2 of TXSTA is HIGH. How i should write the code? Question
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