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chingB
Joined: 29 Dec 2003
Posts: 81
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| Reading a Register of a PICmicro |
 Posted: Sun Nov 07, 2004 5:33 am |
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Hello,
How would you be able to read a specific register of a PICmicro... say, PIC18F452 -- register PORTA?
I understand using :
#byte PORTA = 0xF80 --> can be use to write a certain value to a PORTA register?
Anyone can provide me info or a sample code snippet?
BTW would this be also applicable to other PICmicro register?
Thanx |
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asmallri
Joined: 12 Aug 2004
Posts: 1634
Location: Perth, Australia
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| Posted: Sun Nov 07, 2004 5:46 am |
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Here are a couple of examples. The first is writing to PORTB using the standard output_x() functions. The compiler is responsible for knowing the location of PORTB in the example.
| Code: | output_b(PB_DefData);
set_tris_b(PB_DefTRIS); |
The second methid is more flexible except you need to tell the compiler the location (address) of the register which means the code is processor dependent.
| Code: | byte TXREGM; #locate TXREGM = 0x10 // Transmit Register
//.....
TXREGM = TxChar;
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_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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chingB
Joined: 29 Dec 2003
Posts: 81
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| Posted: Sun Nov 07, 2004 6:00 am |
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Thank u asmallri...
The information you provide would be of great help. |
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dyeatman
Joined: 06 Sep 2003
Posts: 1923
Location: Norman, OK
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valemike
Guest
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| Posted: Sun Nov 07, 2004 8:15 am |
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I prefer to do bit manipulation the following way:
#byte PIC_THIS_REG 0x20 // for example
If I want to set bit 3:
PIC_THIS_REG |= 0x08; // 0000 1000
If I want to clear bit 3:
PIC_THIS_REG &= ~0x08; // 0000 1000
In fact, there is only one assembly instruction generated by this.
bsf or bcf. |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Sun Nov 07, 2004 8:39 am |
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All these examples really show writing. The really simple answer is
| Code: |
PORTA = var; // write to register
var = PORTA; // read from register
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asmallri
Joined: 12 Aug 2004
Posts: 1634
Location: Perth, Australia
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| Posted: Sun Nov 07, 2004 8:47 am |
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| Quote: | | All these examples really show writing. The really simple answer is |
This is only simple for registers that have been defined. By default CCS only defines a few. If you want anything else you end up with the second example being a good fit.
| Code: | byte TXREGM; #locate TXREGM = 0x10 // Transmit Register
//.....
TXREGM = TxChar; |
_________________
Regards, Andrew
http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!! |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Sun Nov 07, 2004 9:56 am |
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| Quote: | This is only simple for registers that have been defined. By default CCS only defines a few. If you want anything else you end up with the second example being a good fit.
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Read his orginal post. He knows how to do that. He just didn't understand that reading a value was just as simple as writing one.
| Quote: | How would you be able to read a specific register of a PICmicro... say, PIC18F452 -- register PORTA?
I understand using :
#byte PORTA = 0xF80 --> can be use to write a certain value to a PORTA register?
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