Mgr. Vojtěch KrmíčekMgr. Vojtěch Krmíček
vojtec@ics.muni.czvojtec@ics.muni.cz
Ing. Zbyněk BurešIng. Zbyněk Bureš, Ph.D., Ph.D.
zbynek.bureszbynek.bures@@unobunob..czcz
PIC12FPIC12F629 / 675629 / 675
Programming PIC in C Part IIProgramming PIC in C Part II
Inline AssemblerInline Assembler
EEPROMEEPROM
Inline AssemblerInline Assembler
Two variants:Two variants:
unsigned int var;
#asm
bcf 0,3
rlf _var
rlf _var+1
#endasm
// or like this
asm(“bcf 0,3”);
asm(“rlf _var”);
asm(“rlf _var+1”);
A #asm block can't be used within any C constructsA #asm block can't be used within any C constructs
such as if, while, do...such as if, while, do...
Timing FunctionsTiming Functions
Frequency of oscillator must be defined:
#define _XTAL_FREQ 4000000
Two functions:
__delay_ms(x) // request a delay in milliseconds
__delay_us(x) // request a delay in microseconds
PackagePackage
EEPROM - basicsEEPROM - basics
Readable and writable duringReadable and writable during
normal voltage,normal voltage,
memory is not directly accessible,memory is not directly accessible,
it’s mapped in the register file space,it’s mapped in the register file space,
direct access via C functionsdirect access via C functions::
eeprom_write()eeprom_write()
eeprom_read()eeprom_read()
address range from 0h to 7Fhaddress range from 0h to 7Fh
interrupt on write complete (EEIF)interrupt on write complete (EEIF)
Functions for Accessing EEPROM IFunctions for Accessing EEPROM I
eeprom_write() initiates process of writingeeprom_write() initiates process of writing
to the EEPROM memory and returns whento the EEPROM memory and returns when
write is completedwrite is completed
new data in EEPROM are valid approx.new data in EEPROM are valid approx.
4ms later ( = 4000 instruction cycles!)4ms later ( = 4000 instruction cycles!)
but next read/write operation waits untilbut next read/write operation waits until
previous one is finishedprevious one is finished
Functions for Accessing EEPROM IIFunctions for Accessing EEPROM II
#include <htc.h>
void eetest(void){
unsigned char value = 1;
unsigned char address = 0;
eeprom_write(address,value);
// Initiate writing value to address
value = eeprom_read(address);
// read from EEPROM at address
}
EEPROM RegistersEEPROM Registers