The 89S52 and 89C51 in ATMEL's 89S52 series have the same functions. The instructions are compatible. HEX programs can be used directly without any conversion. The 89S52 has a watchdog function compared to the 89C51. For other functions of the 89S52, please refer to the 89C52 data.
The specific use of the watchdog is as follows:
In the program initialization, write 01EH first and then write 0E1H to the watchdog register (WDTRST address is 0A6H). The watchdog can be activated.
org 0000
Ljmp begin
Begin:
Mov 0A6H,#01EH ;Send 1E first
Mov 0A6H,#0E1H ;Send E1 later
;Activate the watchdog in program initialization.
……
……
For:
……
Mov 0A6H,#01EH ;Send 1E first
Mov 0A6H,#0E1H ;Send E1 later
;Feed the watchdog instruction
……
Ljmp for
In C language, add a declaration statement.
Add a line sfr WDTRST = 0xA6 in the AT89X51.h declaration file;
code
Notes:
1. The watchdog of 89S51 must be activated by the program before it starts working. Therefore, it is necessary to ensure that the CPU has a reliable power-on reset. Otherwise, the watchdog will not work.
2. The watchdog uses the crystal oscillator of the CPU. When the crystal oscillator stops oscillating, the watchdog is also invalid.
3. 89S51 has only a 14-bit counter. The watchdog must be fed at least once in 16383 machine cycles. And this time is fixed and cannot be changed. When the crystal oscillator is 12M, the watchdog needs to be fed once every 16 milliseconds.
Keywords：89S52
Reference address：How to use 89S52 watchdog
The specific use of the watchdog is as follows:
In the program initialization, write 01EH first and then write 0E1H to the watchdog register (WDTRST address is 0A6H). The watchdog can be activated.
code
org 0000
Ljmp begin
Begin:
Mov 0A6H,#01EH ;Send 1E first
Mov 0A6H,#0E1H ;Send E1 later
;Activate the watchdog in program initialization.
……
……
For:
……
Mov 0A6H,#01EH ;Send 1E first
Mov 0A6H,#0E1H ;Send E1 later
;Feed the watchdog instruction
……
Ljmp for
In C language, add a declaration statement.
Add a line sfr WDTRST = 0xA6 in the AT89X51.h declaration file;
codeMain()
{
WDTRST=0x1E;
WDTRST=0xE1; //Initialize the watchdog.
While (1)
{
WDTRST=0x1E;
WDTRST=0xE1; //Feed the watchdog
}
}
{
WDTRST=0x1E;
WDTRST=0xE1; //Initialize the watchdog.
While (1)
{
WDTRST=0x1E;
WDTRST=0xE1; //Feed the watchdog
}
}
Notes:
1. The watchdog of 89S51 must be activated by the program before it starts working. Therefore, it is necessary to ensure that the CPU has a reliable power-on reset. Otherwise, the watchdog will not work.
2. The watchdog uses the crystal oscillator of the CPU. When the crystal oscillator stops oscillating, the watchdog is also invalid.
3. 89S51 has only a 14-bit counter. The watchdog must be fed at least once in 16383 machine cycles. And this time is fixed and cannot be changed. When the crystal oscillator is 12M, the watchdog needs to be fed once every 16 milliseconds.
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Next article：C51 Storage Type
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