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Download AT89S8252 In-System Programming MCU Application Note
Transcript
Microcontroller ; Counts are reloaded and overflow flags are reset elsewhere. push setb jb cjne dec psw RS0 LT0F, ti2 lt0_lo, #0, ti1 lt0_hi ; save flags ; select register bank one ; skip if long timer 0 overflow set ; test low byte ; low byte is zero, borrow from high djnz cjne lt0_lo, ti2 lt0_hi, #0, ti2 setb LT0F ; dec low byte, skip if not zero ; low byte is zero, test high byte ; both bytes equal zero ; set overflow flag jb djnz setb LT1F, ti3 lt1, TI3 LT1F ; skip if long timer 1 overflow set ; decrement count and skip if not zero ; count is zero, set overflow flag pop reti psw ; restore flags and reg bank zero ti1: ti2: ti3: initialize: ; Initialize controller registers and I/O lines. mov mov mov mov ;; PCON, #0 ; initialize power control register IE, #0 ; deactivate all interrupts SCON, #01000000b; serial port mode 1 TMOD, #00100001b; timer 1 8-bit auto-reload, ; timer 0 16-bit mov TH1, #BAUD_1200 ; timer 1 reload value mov TH1, #BAUD_9600 ; timer 1 reload value mov TCON, #01000000b; start timer 1 mov TL0, #0 ; set timer 0 to max count mov TH0, #0 ; setb TR0 ; start timer 0 setb REN ; enable serial reception setb EA ; global interrupt enable ; Initialize I/O lines. setb DTR_ setb SHUTDN_ setb MISO setb MOSI clr SCK clr RST ; remove reset from target ret 5-93
