Exploring STC 8051 Microcontrollers – Coding
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Using PCA as a Software Timer
We have already seen how the PCA module doubles as timer in the capture examples. However, unlike actual hardware timers, we would have to use some software tricks and keep certain things in mind.
Code
include "STC8xxx.h"
#include "BSP.h"
#define T_Load (1000000L / 12 / 2)
unsigned int value = T_Load;
void setup(void);
void PCA_ISR(void)
interrupt 7
{
clear_PCA_0_flag;
PCA0_load_value(value);
P55_toggle;
value += T_Load;
}
void main(void)
{
setup();
while(1)
{
};
}
void setup(void)
{
CLK_set_sys_clk(IRC_24M, 24, MCLK_SYSCLK_no_output, MCLK_out_P54);
P55_open_drain_mode;
PCA_pin_option(0x10);
PCA_setup(PCA_continue_counting_in_idle_mode, PCA_clk_sys_clk_div_12);
PCA_0_mode(PCA_16_bit_software_timer);
PCA_load_counter(0);
PCA0_load_value(T_Load);
_enable_PCA_0_interrupt;
_enable_global_interrupt;
PCA_start_counter;
}
Schematic
Explanation
This example uses the same concepts as in the high-speed pulse output example and yes, again it is a simple onboard LED blinking example. Between the two examples almost everything is same.
The system clock is set to 1MHz.
CLK_set_sys_clk(IRC_24M, 24, MCLK_SYSCLK_no_output, MCLK_out_P54);
PCA is setup with just as in the past example except for the clock prescalar and mode of operation. In this example, the PCA clock is set to 83.3kHz and software timer mode is selected. Note that since no PCA input-output channel is needed in this example, it doesn’t matter which pin arrangement is initialized.
PCA_pin_option(0x10);
PCA_setup(PCA_continue_counting_in_idle_mode, PCA_clk_sys_clk_div_12);
PCA_0_mode(PCA_16_bit_software_timer);
PCA_load_counter(0);
PCA0_load_value(T_Load);
_enable_PCA_0_interrupt;
_enable_global_interrupt;
PCA_start_counter;
The desired LED blinking frequency is 1Hz and so the PCA0 is loaded with the following count value.
Since we are toggling the onboard LED, every half second, it will change its state and so the toggling frequency is 1 Hz.
Note there is no operation in the main loop.
Demo
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Hi, I am using STC MCU since 10 years. Tech support is ZERO. but they are low cost, very stable. Now I have a problem when the chip that I used is obsolete. Now start to use STC8C2K64S4-28I-LQFP32 but no stc8Cxx.h file, I am using stc8Hxx.h file which compiles but in some stage freeze, the existing firmware. With stc8hxx.h file I can compile STC8F2K64S4-28I-LQFP32 and works not bad
.
I wrote them many times for the stc8Cxx.h file never got answer. Where Can I find that file?
Thank you
Give me detail 8f2k64s281MCU read and write programmer
Give me detail 8f2k64s281reed and write programmer distal
Hi. Can you explain how to use I2C in the slave mode ?
Thanks for these tutorials. I’m getting back into STCmicro coding now, having left them alone for the past several years. Back then I only used the STC89C52RC (and C54RD) but this time I’m also using the more powerful STC15 and STC8 types. Your blogs provide a wealth of useful information.
Hello,
You have done great job with all these tutorials. I am an electronics engineer trying to learn some new stuff. I am located in Greece , Europe and I would like to purchase the development board that you are using and download some datasheets in English if possible but I cannot find them anywhere. Could you please help me?
I suggest you buy from AliExpress or similar platform that is available in your country…. You can find the English datasheet here. English documentation can be found in STC’s official websites such as this one….
Thank you very much for your help!!!
i always get excited when you release new tutorials ,you are really doing a great job i wish i could write code and develop libraries like you.
Well, this is very nice and thorough tutorial indeed, many thanks!
Unfortunately I doubt there is good any reason to learn the STC platform beyond curiosity.
The STC 8051, although pretty evolved from the original 8051 ISA, does not offer anything crucial to justify the relatively high price of these micros and development tools along with certain cumbersomeness of this ancient platform.
They simply can not compete even with the legacy Cortex M0 in any way. I am even not aware about any affordable debugger/emulator for them.
All in all, I would never recommend anybody to start learning/using any 8051 without some very good reason to do so.