[General] Dimmer with PIC16F877A

[chrisss]

Hello, I’m trying to make a dimmer with the PIC16F877A. I found some code and a circuit that I’m testing to use later.
However, I’m encountering several problems. When I start my simulation, the following message appears:

[PIC16 MEMORY] PC=0x0A69. Attempt to write unimplemented memory location 0x008F with 0x71 ignored. [U1].

I’m not sure what the error could be.
Here’s the code I’m using, along with images of my simulation and circuit. code:

---

Code C - [expand]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
/**************************************************************************************
 AC Lamp light dimmer with PIC16F877A microcontroller
 C Code for CCS C compiler
 Crystal oscillator used @ 20MHz
 This is a free software with NO WARRANTY.
 [URL]http://simple-circuit.com/[/URL]
***************************************************************************************/
#define triac_gate    PIN_D2
 
#include <16F877A.h>
#device ADC = 10
#fuses HS,NOWDT,NOPROTECT,NOLVP                     
#use delay(clock = 20MHz)
#use fast_io(d)
#byte OPTION_REG = GETENV("SFR:OPTION_REG")    // get OPTION_REG register address
#bit  INTEDG = OPTION_REG.6                    // INTEDG (external interrupt edge) bit address ( OPTION_REG(6) )
 
int1 ZC = 0;
int16 alpha;
 
#INT_EXT            // external interrupt ISR
void ext_isr(void)
{
  ZC = 1;
 
  // toggle external interrupt edge
  if(INTEDG) INTEDG = 0;
  else       INTEDG = 1;
 
}
 
void main()
{
  output_low(triac_gate);
  output_drive(triac_gate);
 
  setup_adc(ADC_CLOCK_INTERNAL);     // set ADC clock source
  setup_adc_ports(AN0);              // configure AN0 pin as analog
  set_adc_channel(0);                // select channel AN0
 
  clear_interrupt(INT_EXT);          // clear external interrupt flag bit
  enable_interrupts(GLOBAL);         // enable global interrupts
  enable_interrupts(INT_EXT);        // enable external interrupt
 
  delay_ms(500);
 
  while(TRUE)
  {
    alpha = ( 1023 - read_adc() ) * 10;
 
    if (alpha > 9500)
      alpha = 9500;
    else if (alpha < 200)
             alpha = 0;
 
    while(ZC == 0) ;    // wait for zero crossing event
 
    // send firing pulse after alpha
    delay_us(alpha);
    output_high(triac_gate);
    delay_us(200);
    output_low(triac_gate);
 
    ZC = 0;
  }
}
// End of code

---

 

[betwixt]

I can't see anything obvious in the code but I'm not familiar with the quirks in CCS compilers.
You need to find out what is actually at "PC=0x0A69" by looking in the listing or map files. That should tell you which instruction is causing the error. I would guess it has something to do with memory allocation, possibly the code was written for a different processor as address 0x008F (in bank 1) isn't mapped to any pin or peripheral.

Brian.

 

[Aussie Susan]

As you are writing the ZC variable in the ISR but reading it in the main loop, you need to declare it volatile.
Tying \MCLR\ to +5V (in the top schematic) wil lmake it imposible to program a real device. The bottom schematic is better but check the data sheet for the recommended way to connect \MCLR\.
Susan