Hello,
I wrote my first little mcs51 program today, for the Cypress FX2LP. But
I encountered a problem: Timer 1 runs too fast. When I set up Timer 0
and Timer 1 the same, Timer 1 runs about 4 times faster.
I first noticed the problem when trying to do a software UART, which
worked with Tiemr 1, but not with Timer 2.
I have attached programs for a 2-bit counter on the LEDs of my board a
bits 0 and 1 of port A. With Timer 1, the counter increments once per
second.
I compile my programs using
sdcc -mmcs51 test2.c
and put them onto the FX2LP using
cycfx2prog prg:test2.ihx run
Philipp
#include <stdbool.h>
__sfr __at(0x80) IOA;
__sfr __at(0xb2) OEA;
__sfr __at(0x88) TCON;
__sfr __at(0x89) TMOD;
__sfr __at(0x8b) TL1;
__sfr __at(0x8d) TH1;
__sfr __at(0xa8) IE;
volatile unsigned long int clocktime;
volatile _Bool clockupdate;
void clockinc(void) __interrupt(3)
{
TH1 = (65536 - 1000) / 256;
TL1 = (65536 - 1000) % 256;
clocktime++;
clockupdate = true;
}
unsigned long int clock(void)
{
unsigned long int ctmp;
do
{
clockupdate = false;
ctmp = clocktime;
} while (clockupdate);
return(ctmp);
}
void main(void)
{
// Configure timer
// 1000 ticks per second
TH1 = (65536 - 1000) / 256;
TL1 = (65536 - 1000) % 256;
TMOD = 0x04;
IE |= 0x88;
TCON |= 0x40; // Start timer
OEA=0x03; // port A as output
for(;;)
IOA = ~(clock() / 1000) & 0x03;
}
#include <stdbool.h>
__sfr __at(0x80) IOA;
__sfr __at(0xb2) OEA;
__sfr __at(0x88) TCON;
__sfr __at(0x89) TMOD;
__sfr __at(0x8a) TL0;
__sfr __at(0x8c) TH0;
__sfr __at(0xa8) IE;
volatile unsigned long int clocktime;
volatile _Bool clockupdate;
void clockinc(void) __interrupt(1)
{
TH0 = (65536 - 1000) / 256;
TL0 = (65536 - 1000) % 256;
clocktime++;
clockupdate = true;
}
unsigned long int clock(void)
{
unsigned long int ctmp;
do
{
clockupdate = false;
ctmp = clocktime;
} while (clockupdate);
return(ctmp);
}
void main(void)
{
// Configure timer
// 1000 ticks per second
TH0 = (65536 - 1000) / 256;
TL0 = (65536 - 1000) % 256;
TMOD = 0x01;
IE |= 0x82;
TCON |= 0x10; // Start timer
OEA=0x03; // port A as output
for(;;)
IOA = ~(clock() / 1000) & 0x03;
}
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