Hi, I want to access the ADC0804 which is connected as the memory mapped device at 0x0001. Initially, I want check whether, address and data bus is working fine. For the same, I wrote the code as :::::Program 1::::: #include <p89v51rx2.h>
volatile unsigned char xdata *p = (char xdata *)0x0000; sbit LED = P3^0;
void main() { int j = 0;
while(1) { p[0] = 0x55; for(j=0; j<=2500; j++); LED = 0; p[1] = 0xAA; for(j = 0; j<=2500; j++); LED = 1; } }
:::::: Program 2:::::::::::::::: #include <p89v51rx2.h> #include <absacc.h>
volatile xdata at 0x1000 unsigned char config; volatile xdata at 0x1001 unsigned char config1; sbit LED = P3^0;
void main() { int j = 0; while(1) { config = 0xAA; for(j=0; j<=2500; j++); LED = 0; config1 = 0x55; for(j = 0; j<=2500; j++); LED = 1; } }
Program 1: LED Blinks but, there is no ALE or BUS transisitions. Program 2: Compiler through error that missing ; before 0x1000. This code I have refered from one of 8051 SBC webpage.
Kindly let me know what is the wrong? Is it, I need to set something in compiler? Iam using Keil uV4.
With thanks...
Provide me complete C code... Nopes. Its your job to write a code to interface ADC.
Hint: !EA pin. Read datasheet of 8051 and figure out the starting address of the external memory depending on the status of !EA. Then compare it with the address you are initialsing in the xdata pointer.
Thanks... I agree that writing program is my part. But, Since, I am purly hardware designer and just started coding, I could not able to think 100% software points. So, If I get some example to access external memory mapped devices (basically, initialization and writing/reading to one location, it will be helpful to continue further.
I am using P89V51RD2 from NXP.
With Thanks...
Then compare it with the address you are initialsing in the xdata pointer. !EA doesnot have any relation with xdata. if, !EA =0, external code memory is accessed. hence, toggling of address and data bus can be seen (helps verifying if the external buses are working properly or not). also ALE and PSEN toggle.
Hint: !EA pin fatty sausage + male cow manure
Erik